After spending the afternoon with iOS 7, I'd have to say my biggest disappointment focuses around the app updates. Most of the apps I've seen that launched new designs are simply ports of recent Holo releases for Android. I was expecting something new and refreshing in app UI's, but most of the apps I use look exactly like they do on Android now. Which is a good thing, but still. Maybe it'll just take them some months to start deviating a bit.
Apart from that, I'm still surprised they haven't addressed any of the UI inconsistencies (random font sizes, opacities, shapes, etc). The new features are a welcome addition, but overall this has been a pretty "meh" release for me. Definitely more surface-level than I was hoping for.