I'm running it on my iPhone 5 and I'm seeing very little in the way of actual lag, there is some, mind you, and more than there was in iOS 6 (not much more though), the main problem is the speed of the animations. Most of them are just too slow- transitions that were quick and snappy on iOS 6 now take far too long. It's probably only milliseconds difference, but yes, the apparent speed of navigating the OS feels slower. Not a lot slower, but enough to irritate me.
Apple certainly has some work to do, hopefully everything gets tightened up in a point release soon.
Interesting. Thanks for sharing that. I do hope it gets better too.
I have (had?) high hopes for the future of iOS especially when it comes time for a larger screen iPhone, whenever that may be.