beta 3 is the first version of iOS I've installed on my iPad3.
Overall, it's nothing I wouldn't expect from BETA software.
The UI is a bit laggy, seems like it's struggling with the retina graphics, even the parallax is stuttery. I've noticed parallax has a pretty high latency even on iPhones so it kinda makes me feel drunk after looking at it for a while.
Photos crashes when trying to view photo stream, a few misplaced fonts in the settings app, and I can't change the timezone from GMT.
Most 3rd party apps work fine, the only one that doesn't work for me (that I've found so far) is Pulse.
I'll be submitting a few bug reports but when I'm finished testing my company's web apps I'm probably going to revert to iOS6 until a few more beta revisions of iOS7.
To everybody that's having problems, you're supposed to submit bug reports. That's why you're beta testing iOS7!