Ab wheels work awesome... I havent used this one, but it's basically all the same crap. try doing 3 sets of 5 reps on the wheel and youre hurting the next day! it doesnt only work the abs, it works your tricepts, shoulders and all sorts of stability muscles. Compound exercises are the best, I think.
If you don't have a "wheel", get into position on your kitchen floor or any surface that is slippery and place a towel in front of you, place your hands on the towel and push out and pull in. This exercise may be a little more difficult then the wheel, because of the friction. Use a wheel for awhile to work on your form, then mix it up with the towel pulls.
enjoy.