A little background
Before I start, don't get me wrong - I understand (I think) the direction that the site is going in and why you are doing the Area 51 thing. However, in the back of my mind I have a couple of ideas that I would like to raise.
I found out about Stack Overflow about a year ago and tried to answer questions, but as an IT professional, I wasn't really answering that many. I then found out about Server Fault and liked it much more, but I am mainly Wintel (and a bit more), and found myself skipping about 80% of the questions as I am not a real in-depth *nix guy. Then, Super User launched and I haven't been happier in a long time!
Since I found Super User, I try to help as much as I can. But at the moment work is very busy and as much as I would like to look at all the trilogy sites, I just haven't got the time.
I have seen, that on Area 51, the Web Applications proposal has gone through. I am happy to help out where and when I can but at the same time, I am thinking to myself, do we really need a separate site?
Do not get me wrong, I want to see a Stack Exchange site for every topic, but I just can't imagine going to 5+ websites every day to answer questions.
My idea is, I want to help out people on Stack Overflow with general web/jQuery (amongst others), Server Fault on Windows Server and telephony type questions, Super User on most topics and this new web application site.
So, to sum up, what I suggest is to get one interface that just lists all questions from all sites on selected tags / topics that you select. Reputation in the bottom corner of the answer would be your Total reputation from all sites (like how Area 51 does it). Then people can click on your name to get a "tarted up" version of the accounts screen. It can list where your expertise is by how your reputation is made up.
I hope you get the basic idea and I haven't gone on too much. To sum up, I want to help out no matter what the site as long as the questions are in a field I can help with. My main reason for writing this is I think there are so many fields (Web Applications, Mobile (smart) Phones, PDAs, Devices) which 80+% of the members would like to see / try to answer but may be put off checking many different sites.
... I think it may be to much of a change at this point, but I really want to see feedback on this and whether I am the only person who feels like this - or is this something someone can create out of the API?