The Kopp/Joana guides were great for Vanilla/BC.
The Extreme Leveling, was good for solo but not so great for boxing in WotLK.

Haven't tried the Zygor one, but it seems the best rated.

Not even sure I'll buy a guide this time around, but 30 bucks or whatever isn't much.
And I didn't do the beta, and do like to have an idea of where to go, etc.