I’ve been using it full-time for well over a month. It’s solid on the iPhone. (I hardly use my iPad, so I can’t judge that version, but I hear it’s a bit less solid.)
It took me a few days to get accustomed to the new look, but after that, I loved it. Beyond the appearance changes, I’ve been greatly enjoying a lot of other features that I thought were stupid during the keynote, like Control Center.
Give iOS 7 a chance and let the new look sink in for a few days before you judge. You’ll probably like it. And then you’ll see iOS 6 somewhere and think, “That looks so old.”