There are guest passes that allow you to try out the game. There's a thread here where they are being given out. This way you can see if your computer can run it.
...Although it would be nice to see some deals on this game.
Sent you a guest pass. Go to starcraft2.com/guest to redeem it.
I thought my laptop would be able to handle it well, but it doesn't. It over heats like a bitch. I have to put everything on low . Oh well. The game is still fun either way, so I'm not gona complain.