I took the regular Kaplan on-site course (and supplemented with a few of the
Manhattan GMAT books) and was very pleased with it, and all the online material that came with it. I would highly recommend their services. As for the advanced class, I can't speak to it, but if you have the fundementals in place, I think it could be good for you.
By the time I was done with the basic class I was going over as many advanced concepts as I could. I went from a 570 Diag (this is why i didn't do the advanced) to 710 on test day 9 weeks later.
PS, if you have the opportunity, I would definitely use the "test day experience" that they offer. It can be a little bit of a challenge to set up, but I would recommend taking it a week before your actual test. You basically get to take a kaplan practice test at the ACTUAL TESTING center. The intangibles I gained from that experience were priceless.
Good luck to you!