Yes, it will work on the 2008 Mac's (I bought the downloadable version from Blizzard a few months ago). I bought my older model MBP in November (Early 08 version) and it runs fine. My sig block contains what type of MBP I have. Hope it works for you as well as it does for me!
EDIT NOTE: Here is the configuration on my MBP: 15.4" display running 2.5GHz Core 2 Duo, 2GB RAM, 250GB hard drive, GeForce 8600 w/512MB