Fair disclosure, iOS 7 is nothing new to me; I've been running the beta on my phone since June, but now that it's out in the open we can all have a chat about it. What is good, what is bad, what hasn't really changed?
Initially, I will admit that I wasn't a fan of the "flat" design. I thought I wanted it and I know I hated the skeuomorphism in specific apps in iOS 6 but I'm not sure I was ready for such a drastic change. As with all new things there is an acclimatization period and once you get by that hump, everything seems to be a little more natural.
That hump, in question, was about two weeks into the experience for me. One day I picked up my phone and didn't dislike the design as much as I did the day before. Gradually, I've grown to like it more and more until now, I am quite used to it and looking at iOS 6 just makes the UX feel antiquated and in need of a revamp.
When adopting iOS 7, I consciously removed all of my beloved replacement apps for the default Apple apps. I missed some of them; chrome, fantastical, cobook, mailbox and a couple of other ones. The only one that has made a return to my home screen so far is cobook which replaces contacts. If you don't know about cobook then I highly recommend you check it out. It that's a review for another post.
The bottom line, I think, with regards to iOS 7 is that it's here to stay. Are there people out there who don't like it? Sure, that's an inevitability but an adoptions ate of %60 after only a week speaks volumes as to the popularity and effectiveness of Apple's rollout. So if you were on the fence about upgrading, I say go for it; stop hesitating and just do it, you won't be sorry.