Mabs - SC2 is split into 3 packs - terran/protoss/zerg - w/ around triple the content of original SC ( so about the same amount of stuff - but only 1 race per box ).
Yes - but each has as much singleplayer content as the original SC ( Only SC2 Wings of Liberty is available atm - I think the zerg or toss pack gets released in 6-12 months ).
I won a Starcraft Battle Chest back in 1999 which was the game, add-on and strategy books.
I installed it, played it twice, uninstalled it.
It put me off RTS games for life. I've never played an RTS game since.
The one and only thing that was any good was the "Receiving incoming transmission" wav. That's been my SMS notification for years.