This ab workout is excellent. The range of the moves really tests your core and is good for lengthening and strengthening, which is a new challenge altogether. I found the first of the three workouts to be a little easy, but it's a great intro to what is to come for the next two, which have very advanced moves. As always, she is a pro when it comes to injecting cardio spurts, so it makes for an effective 30 minute workout. Get it! I love Jillian's 6 Week 6 Pack DVD as well.
If you want something that will cause you lots of ab pain from the most gruelling ab workout with weights, get Bob Harper's "Totally Ripped Core" and give yourself 2 days minimum to recover from it! Your legs will be sore too because Bob uses tons of squats in all his workouts.