Well, after playing about 10 games (1v1 + 2v2) I can say that SC2 will be my new addiction. Really nice game :D The new Battle.net is just quality as well, it's the very thing GFWL should have been.
Only played as Protoss so far (easily my fave race) and I haven't been able to spot any glaring imbalances. In DoW2 beta within like 4 games the imbalances were abundantly clear. That's not to say there isn't balance issues tho, I'm just not skilled enuff yet to make a qualified judgement. Plus I was way too excited to care :D
Opted-in about a year ago, like when the option first came available, all I got to say is JUSTICE! Bout time I had some good luck.