. Period. Just do it. Don't let anyone tell you different.
Slightly more expensive, but the incremental gain in quality is completely worth it.
Read them, absorb the knowledge and then do the official guide before assessing whether a course is worth it or not. If it still is then you've at least narrowed down your weaknesses and will be able to maximize the value out of your prep-class.
G.T.L. - GMAT, Tanning, Laundry
Round 1: 05/12/10 handling-a-grenade-thesituation-s-official-debrief-94181.html
Round 2: 07/10/10 - This time it's personal.