Six Week Six Pack

Well, obviously it targets your core. She keeps you moving from standing abs to exercises on your back to exercises on your stomach to planks so you'll hit every muscle in your core plus a few that you didn't know you had. She throws in things like plank jacks, burpees, and mountain climbers to keep your heart rate up, so it's also very aerobic. You'll also feel it in your arms and in your legs on some of the exercises.
As far as format, it's basically one giant circuit that you go through twice. She takes it nice and slow the first time through and explains things really well. The second time she speeds it all up so you're just flying through to the finish.
It's hard, but the next day my core felt awesome. All of my muscles were nice and firm, and my waist looked smaller. Bottom line, I think this workout will really give you a strong core. Considering that it's Jillian, it's pretty intense, but since it's a shorter workout it's definitely do-able. Besides, if I can feel that awesome the next day then it's a keeper.