I(')ve used iOS7 on my primary phone and ipad since beta1.
Everybody is griping about the rainbow colors, Apple made a big mistake in the presentation of iOS7 they chose the wrong background image. (see ugly section)The good
The transitions when you navigate is very good. When you click a folder it "zooms you" into that folder, click an app in that folder, and you go one step further in. Click the home button and you are zoomed one step out, and go out of the folder you take a step out to the home screen again. This actually gives a reassuring feeling of walking in a door, and you always know that the home button, walks you out the same way you came in. It gives the impression that you are drilling down in the layers and back out again. This is actually the beginning of 3D navigation UI, which as phones get more and more functions might make sense.
I really like the overall look and feel
Color, yes I like the colors! The way that what you choose as a background picture makes changes to the whole UI of the phone. Makes it very personal. (also see ugly section)The bad
Change. Change is always bad, and I dread the day my 60 year old mother upgrades her iPhone. There will be a support call to me.
What is clickable. Almost always color lets me click on it, but not always.The ugly
Choose the wrong background image and your phone is an unreadable mess. Choose the background picture that (I presume) Jony chose for the presentation, and your phone looks like an episode of My Little Pony
Lists. Entering dates and times, used to be nice looking understandable wheels you scrolled with your finger. Now you have floating text you manipulate with your fingers. What makes it really ugly is that all drop down lists are navigated this way, and web form designers love their drop down lists, making it a horrible experience on a lot of web pages.