I'm actually in the reverse situation--I read the CS edition, but have CS2. Based on that, I'd say it's absolutely useful across versions--the bulk of the info is not related to version-specific controls, and the parts that are should be simple to figure out. If you're headed to CS2 anyway, it would make more sense to get the CS2 book than the CS version.
You could also see if your library has a copy of the CS version, and browse through that for some of the CS-specific bits?
Overall, an excellent resource--I even found the concepts applicable to using Pixmantec's RawShooter.