I just installed it last night and it is not laggy, and I didn't brick my phone. I did get a weird error message that had to do with my SD card and that I haven't seen on the forums, but I worked it out. I think I will do a post about that.
It's pretty good, the only blip I notice is some lag pulling down the action center from a locked screen, and that is only occasional.
There are other things that are bugging me--I can't set up Cortana because the screen with the acceptance button at the bottom won't scroll for me! So I can't proceed past the initial "Let's get some info from you first". Also, I am hacked that I have to do that at all, what happened to my notebook from 8.1? So that's a bummer. Can't see my schedule on the Outlook calendar live tile unless I use the largest size, which I don't love. Little stuff like that, but I am really enjoying playing around with it, it's got some cool stuff for sure. It's got a definite learning curve.