I still really dislike the new icons including the new 3rd party app icons. They look like cheap clip art vector from the 90s now, really hideous "plain" style.
The music app is ruined on iPad, the gorgeous 'album' view was removed for absolutely no reason, and I fight with it on iPhone, it's just unrefined, hacked. The "ratings" button is where the "back" button should be, please?
Text as buttons is a horrible UI decision I find myself taping text sometimes to see if it does something. If the founders of AHIG didn't pass away already, they would have after trying iOS 7
Folders on iPad show 9 items, is this a joke?
The notification center is slow and has horrible UI. I tried Android's equivalent the other day and fell in love with it, it has a much clear presentation and function.
The animations are slow. I'm on 5s and I take a huge responsiveness hit. Good thing one can sort of deactivate the slow zoom in/zoom out with "reduce motion" setting, but still it's a poor default decision to have them.
The 'Picker' control (number slider in clock app) isn't as responsive now, it sort of goes over and doesn't stop sometimes when you tap it to stop rolling.
I could go on, there are other unrefined things.
I do agree with others that when going back to iOS6 it does seem old and last season, but guys remember this is like fashion, we are being told this is the new hype thing, it's not necessarily better.
It's a fashion cycle, 10 years from now there will be some new theme, and this "plain" theme will look retro. There is still no way I'm liking plain clip art icons from the 90s better than what we had before.