Yeah, I did the dirty deed and installed steam for this. I actually got to play last night. Not only that, but Games for Windows Live is double teaming this with Steam. Good news is if you have an Xbox Live account, you can use that. Bad news is you have to launch it through Steam (not sure about retail, but for the beta this is certain).
It includes all four races, all five launch maps, and Live Trueskill matchmaking. Also, you can set all your opponents in a custom game to AI and it works like a skirmish.
I have to say, as of now, I kind of feel like the Space Marines are underpowered. A tactical squad costs quite a lot only to receive 3 un-upgraded marines. Furthermore, SM Vehicles cost a lot of power. It's hard to field an army of SM's. Also, don't get used to destroying everything with three squads of marines (see Dawn of War I). When you upgrade them, they become very specialized (Anti Infantry OR Anti Vehicle). Same goes for Dreadnoughts. You choose to have either Assault Cannon Capability OR Melee Capability.
Everyone seems to like Tyranids, and at the moment they seem to be a little overpowered. Very easy to field a large army with.
The Beta includes full VOIP support. I didn't even know this until I had my headset on, angrily asked for some help (was talking to myself), and I hear some guy say "ALRIGHT!"
The beta will be open to everyone on the 28th, so if you don't have SS, don't worry about it just yet. You'll have plenty of time to play before release day.
Can I play beta through LAN as well? Cause I really wanna try this game with my freind in home.