The Kaplan program is pretty good. Really, I think any "major" program is going to be okay if you're mainly looking for structure/monitored study.
I will say this, though - the ONLY criterion for teacher hiring by any of these outfits is scoring high on the GRE (usually top 5%), followed by *maybe* thirty hours or so of training (Kaplan has five training sessions plus "prepping" the teaching material over the course of about one month (a 3-4 hour session once weekly), for example). If at ALL possible, do your research and make sure to get an actually *good* teacher if you're going to be spending money.
If you have friends who've prepped with a course, ask them if it was worth it and who the teacher was, and try to go with that. If not, ask the sales person about whatever benchmark ratings the instructor has (I know Kaplan benchmarks instructors); bear in mind though that these outfits benchmark with post-class surveys, so they aren't *necessarily* reflective of teacher ability.
tl:dr: There is no regulation or oversight of test prep *at all*, so there is a heavy "caveat emptor" involved... sort of like hiring, say, a tarot reader:embar:
That said, using a course for pacing of intensive self-study isn't a bad idea - just bear in mind that practice/practice/practice is key!
(Disclaimer/Source: I used to teach test prep courses - easy money! I got a perfect score on the GRE: great for marketing. That said, I *did* make an effort to teach well! Not all test prep folks do.)