I've been running it for a while now. Haven't had any issues. I've updated my Mac Pro and MacBook Pro without any issues. I've got a bunch of friends on it too without problem. It's not a very large update and doesn't seem to introduce too many breaking features. Some weird file layout issues with Coda (if you happen to use it), but that's literally the only issue I've seen and I'm sure Panic will update Coda soon (if they haven't already).