one of the best games in its genre.
advancing through the tech tree. One of the reasons that this is THE RTS to buy, is that all of its individual races actually have some amount of difference to how you go about advancing through the tech tree.
the protoss must build pylons to build buildings within its energy field. the zerg produce combat units via larva which hatcheries build many of ( still have to pay for the evouloution.) and terran buildings can hover off the ground. so for all intents and purposes i believe the protoss are best for steamroller tactics, provided you can distract your opponent with some battlecruisers for cannon fodder. the terrans are good for expansion and scouting due to their ability to hover buildings. and the zerg are good for steamrolling, but to a lesser extent are better for scouting.
and the campaign mode is excellent, but the real reason to have this game is for battle.net which is an excellent online resource that i really wish blizz would open up some deals for it to be open to other devs for a price.
map editing is awesome and unlike warcraft 3, it is actually included in the game menu so you dont have to waste your time with C:/programfiles/starcraft or whatever.
it is a must buy, untill starcraft 2 comes out :)