I finished my GMAT class last fall, but didn't have time to finish all the out of class material during the course of the class (work).
Finally, from April-June 2009, I buckled down and finished everything.
GMAT Dec 2007 (after finishing a diff prep program): 610
Highest score on any practice (including 2 GMAC practice exams): 680
GMAT Jun 2009: 710 (48,38)
I can say with assurance that the materials provided by the MGMAT company (books and online resources) really helped. I felt the MGMAT class not only focused on the proper topics/subjects, but also focused on strategies that would supplement those topics/subjects.
Many Thanks,
Muhamad