Instead of useful features, layout update contained bobcat. Would not buy again.
The activity page used to look like this
Note the efficient use of space, with nothing squished into an overly-tiny space or stretched out to fill an overly-big space. Note the ability to switch between the summary/answers/questions/tags/badges/bookmarks/following/bounties/reputation/all-actions/responses/votes panes from at or near the top of the page, without having to scroll up and down to see the whole switching menu.
Note the lightweight question/repchange/answer markers, showing where your highly-regarded questions and answers are and where you've been gaining or losing reputation lately, without cluttering up the page with information that can easily be had by following the provided links. Note how this allows lots of information to be compactly summarized in the summary tab without taking up an inordinate amount of space.
Now it looks like this
Note how the three boxes of the summary segment of the summary pane have been squished into a space too small for them to comfortably fit. Note how the switching menu, now that it runs vertically down the side of the page in the column freed up by crushing the summary pane, runs off the bottom of the screen, necessitating scrolling down to see the whole thing. Note the oddity of putting more things side-by-side, producing cramping issues that will be even more severe on narrower screens, when the intent of the design changes is ostensibly to make the desktop site more mobile-(and-thus-narrower-screen-)friendly. Note also how the blue square on the bookmarks tab (and presumably the other tabs of the pane switcher) is now a smaller circle that crowds the edges of the number inside it and makes it harder to read.
Note how the segments of the summary pane have grown ridiculously huge in order to ensure that there will only be room for a single column of said segments. Note the enormously-increased amount of scrolling that simply scanning the summary pane for some information found in one of the later segments now entails.
Note how the tags segment, in particular, now consists of a single column of tags on the left, some tag stats on the right, and a huge block of empty space in between. Note how, in addition to this, the individual tag entries have been blown up to match the size of the question and answer and repchange and whatnot entries - specifically, to match their new, inflated size. Note how, as a result, the tags segment now takes much more space to convey a little more than half as much information as it used to.
Note how, due to the use of a sidebar to house the pane-switcher menu, we now have a whole column of blank space over on the left which does nothing but shove the segments of the summary pane over to the right, leaving them with too little remaining screen width to comfortably accommodate a second column of segments, yet still far more than needed for a single column. Note that width restrictions on mobile devices could have been better accommodated by leaving the pane switcher as it was before (thus freeing up precious screen width for the segments themselves), and dynamically shuffling the segments from two columns into one on screens too narrow to comfortably accommodate two side-by-side columns of segments, without ruining the page for desktop users whose screens could easily accommodate two columns side-by-side.
Note that, presumably as (yet another) bad effect of blowing everything up to hugeness, the repchange bar chart is now borked. Note, firstly, that the individual bars are now crammed tightly against each other despite having more room to spread out; without the thin whitespace that formerly separated adjacent bars in the chart, bars of the same or similar height next to one another could potentially merge in the viewer's eye, causing confusion. Note, secondly, that the taller bars are now whacking their heads on the gray border at the top of (and also surrounding) the segment in question.
Summary: 0/10, would not buy again. (Boo!!! Hiss!!!)
System: Chrome 96 on Ubuntu 20.04 LTS x86-64.
Sometime in the past 20 hours, the layout changed slightly. Now the Questions and Answers segments are narrower and side-by-side, somewhat reducing the amount of scrolling needed, and it looks like some of the other elements may have been shrunken slightly as well. However, even at their smaller size, they're still bigger than they need to be; other segments desperately in need of side-by-sideness (tags, for instance) are still single-file; there are still unnecessary gray borders around everything that do nothing but take up space; and the new question-/answer-segment side-by-sideness further highlights the problems with the vertical pane switcher, as the width it takes up, and the resultant reduction in screen width usable by the segments next to it, causes the question titles in the question and answer segments to be cut off short enough to often make it impossible to figure out at a glance just what the question is. (Not helping matters is the completely-unnecessary question-date label at the far-right end of each of the question/answer bars. The date of a question I asked is easily found by going to its question page; the date of a question that I answered is completely irrelevant for my purposes, since what we're interested in here is the answer I wrote to the question; and, in both cases, it forces the question name to be cut off earlier than otherwise.)
New summary: maybe 1-2/10. Still awful.
Things have marginally improved, with the tag and reputation segments now also supporting two-column viewing; the narrowing from going back into two columns also seems to have incidentally unborked the reputation graph, which looks to be back to its old self:
Note, additionally, how the question titles in the reputation segment now wrap instead of cutting off, which is a nice feature.
- The tags segment still has far fewer tags visible than it used to, and, thus, manages to still contain considerable whitespace despite its much-decreased width.
- The space-wasting gray borders which force the entries in each segment further apart are still there; removing those borders would easily free up enough space to enable the question titles in the question and answer segments to wrap (as has now been done for the reputation segment), rather than being cut off.
- The side-mounted pane switcher is still taking up precious screen width and making an entire (fairly-substantial!) column of the screen unusable by anything else. Just look at the huge vertical white bar on the left side of the screen:
- The side-mounted pane switcher also still requires vertical scrolling to reach its lowermost items on most screens. Although you said that you implemented the vertical pane switcher to avoid the need for wrapping the pane switcher if more panes are added to it in future, the cure is far worse than the problem; keeping the previous, horizontal, pane switcher and allowing it to wrap around onto two or more rows would have taken up a marginal amount of additional vertical room, while (unlike the vertical pane switcher) not requiring scrolling to see the whole switcher or crushing the rest of the page laterally.
- The remaining segments of the summary pane (bookmarks, followed posts, accounts, bounties, and votes cast) are still single-file-only, and thus still horrendously space-wastey on wide screens:
- The new graphics in the badges segment are gorgeous... and belong on the badges pane, not the summary pane! A simple list of my latest few badges would be sufficient for the badges segment of the summary pane, while the badges pane would benefit enormously from the gold/silver/bronze graphics currently found in the summary pane. As a matter of fact, I'm not sure that the summary pane even needs the badges segment at all, given that there is, and has always been, a display of my total gold/silver/bronze badges right at the top of the summary pane, including both my newest badge and the one I'm closest to earning next!
- And, even with the reputation events from more than a few days ago now being collapsed by default (like they used to be), the reputation pane is still horribly space-wastey - I'd like to be able to see more than just my past three or four reputation events without having to shell out 10 grand for an 8K monitor, peeps!
Current assessment? Maybe 3/10, would still not buy again.
My recommendations at this point? Honestly, I'd say the best option would be to revert the layout update completely and go back to what the layout was on 6 December, except with the addition of summary-pane dynamic segment columning (segments automatically reshuffle into two columns on wide screens, and one column on narrow ones) and summary-pane question-title wrapping (question titles wrap instead of cutting off, like what the reputation segment currently does), as well as the ability to wrap the horizontal pane-switcher (if that hadn't already been implemented). EVERYTHING ELSE about the new layout is a net negative, ESPECIALLY for desktop users, and needs to go ASAP.
Note: I am aware of the irony of me complaining about (among other things) the need for a vastly-increased amount of scrolling... in an answer which requires a great deal of scrolling. :-p Nevertheless, I judged the multitude of screenshots to be necessary for illustrating the points made in my answer, unlike the necessary-for-absolutely-nothing whitespace and padding and added borders and single-columning added by the layout update.