Starcraft rewards skilled players and there are sure to be plenty who have the experience and have watched the battle reports enough to come in and quickly get come up to a solid skill level at playing the game. That sets up the classic confrontation of someone less adept jumping into an early game and wondering what hit them not long after when they've been wiped out. It's definitely happened to me. I can enjoy the single-player only to find that when I get in multiplayer I'm sub-scrub. So one of the big things I want to see is how well its matchmaking adapts to pitting me against people with whom I can have a good game.
It's sort of like seeing how well we can pick the right Shacknews stories for ER, like these:
AvP is 15 GB because the DX9 and DX11 assets are separate?!