I did two rounds of Body Revolution. Loved it! I would say it is more for toning and weight loss than it is for building major muscle (nothing like STS or XTrain). Jillian only uses up to 8 lb dumbbells in the program, but I definitely went heavier on a lot of the exercises. I would say I toned up quite a bit and saw great improvement in my core strength and definition. I know some people don't care for Jillian's drill sergeant attitude, but I like it, and she really isn't that bad in this program. Really loved the big group she uses...you get attached to them by the end of the rotation! Definitely check out Jen's review...she is spot on with her comments and descriptions!