From what I've read, most say it runs pretty good. (As good as 1.0.1 or slightly better) But as always with any bit of software, there are the few unlucky that doesn't run so good.
Devs will probably see a GM Wednesday. The official public release can't happen until iOS 9 is officially released to the public. And that isn't usually until a couple days before the new iPhones are available. (Roughly a week after the keynote)
Running OS 2 here. It does not run well at all. Replying to a text locks the watch up for around 30 seconds before you are able to do anything. Siri is all messed up with delays etc. It is no where near a GM.