The new Battle.net is cool but since we are in Beta I can't tell if they don't have all the features implemented yet or if they are simply not going to be there. The biggest red flag for me is no chat room so far. I think that was a huge part of the original B.Net community and I think Blizzard would be very unwise to leave it out. I'm hoping it's just not implemented in the Beta yet, there are currently alot of buttons on the Menu that you can't access yet. I will look into it more later.
SC2 it's self is exactly what you would want SC2 to be. It takes everything that worked in SC and just builds on it, this is why Blizzard is the king. My only bitch thus far is the game is really dependent on counters. You have to know which units are good against what enemy units and be willing to completely change your strategy and army makeup at the drop of a hat. It isn't bad because of how much the battles change, and if you don't change you will lose, but I don't like that certain units just have NO chance against their counter.
I've currently played around 50 games since Friday night. I just started on the Ladder and I'm 7-1. I was ranked 12th in my Platinum league when I logged, which doesn't mean I really good just everyone else is really bad.
As far as playable beta's go and fun factor. SC2 gets a 5/5. I've played it until 1-2AM Friday and Saturday night and after succumbing to exhaustion I went to bed around 10:30 last night only to wake up at 3AM wanting to play. I'm sucked in, just as bad as the first time I played SC or SC:BW.