I'm using iOS 6.1.6 on an iPod Touch (4th gen). The mobile Stack Exchange sites work very well, except for a few quirks.
First, if I'm not logged in when I visit the site and get logged in automatically, the pop-up that tells me to refresh to log in is located at the bottom of the page. I have to scroll all the way down to see it:
Once I'm logged in, the notification menu and the reputation menu have an overlap problem. They look good when you first click on them, but as soon as you scroll down, they are transparent, showing the page behind the menu:
Both the notification and the reputation menu act like this, but the "bubble" stack exchange menu doesn't have this problem:
None of these are major problems, just minor annoyances, and I haven't found anyone else reporting this yet. (Apologies if I missed it.)