Well I for one love it! An OS that is fitting for a beautiful bit of hardware (iPhone 5). I actually like a lot of the design choices used anyway, translucency, matte looking colour, white (I have a white iPhone) and I think the new app switch will actually make people 'want' to use it more often because it just looks cool. I know people who just don't care about app switching, they just find the app and re-open it..
I love the fact that the OS makes use of the full screen in Safari and elsewhere. Sure it already does it in iOS6 but it looks more refined and used more often in iOS7. I mean, it's still a tiny screen, we need to make full use of it, I like how everything seems to recline away leaving just what you need to see.
My one gripe? I suppose I didn't expect the icon / home page basic look to change at all but ... it might have been nice for them to "think different" in this case. I wouldn't have minded is all. It's still fine, and the way the wallpaper looks 3D is a very cool flourish. The moving wallpaper very cool too even though it's not a new concept. It definitely suits iOS though. ;)
That said, I'll really know once I get it on my phone, and especially looking forward to trying it on the Retina iPad Mini (when they finally announce the thing!).