I have the Ab-Lounger Ultra. Had it about a year and a half. For a shorter person like myself, it's rather uncomfortable. I rarely use it. However, I have the Ab Roller which is quite effective. I can do crunches, reverse sit ups and side crunches for the obliques
I love it!
What I do is kinda silly though
I have a series of books that I have already read, but love. So I am reading them all over. I do 10 crunches and then "reward" myself by reading a chapter lol. By the time I am through reading for the evening, I will have done 7 to 8 sets of all 3 positions