On iPhone 4S...
Used it since Tuesday.
Lots of bugs, saw most on the lists from search "ios7.0 bugs". My #1 is : Unable to see all of calendar event notes which is really annoying and detremental to my day job as my office uses Lync for calendar event creation and using Lync app is somewhat inconvenient sometimes.
Whole OS crashed 3 times yesterday. Also have had to kill unresponsive core apps such as phone and calendar.
Slow keyboard response time. Hate the colors. Phone heats up, battery life horrible, had to plug in around noon, usually don't have to until bedtime. Left/right swipe on Safari only works with left index finger (I don't know why, maybe the swipe sensitivity is messed up in their code), not right thumb - which is how you have to do it since they removed that bottom bar (or touch top bar and THEN use bottom bar, incovenient).
I do like the improvements they did make, mark all, call a message contact, etc.
Switched back to 6.1.3 just now. This was my 1st install of beta os, so this all may be "typical". Hope apple corrects a lot of these issues.
Might just be 4S. Users here should also tell you what device they have this on.