On a side note, the opponents can see Terran command center scans, which is a bit strange. Opponents can also see the red/blue (team color) dots that indicate the range of a sensor tower. The sensor tower covers a really, REALLY big area, with the tower at the center, so some strategy has to be used in tower placement. Also, as the person that placed the tower, you don't see which color team enemies are attacking - they just show up as red dots - a slightly different red, if you happen to be the red team, which is a tad bit confusing.
I have one more "practice" round, I guess. I kinda feel bad about not playing more, since there's SC fans out there dying to play SC2. But I enjoy co-op against AI's more, but that's not an option. And I'd rather play against friends, 'cause I'm not a really skilled player... And there's no campaign mode in the beta.
Overall, it's similar to Starcraft 1, with some different units (and less units).