I don't have an ab lounge ultra, but the setup looks like the ab roller (which I *did* own), ab rocker, etc. ~ basically something to support the rest of your body while you do your crunches. The workouts you can do with these devices are quite limited and you're bound to be bored pretty fast.
Unless you have major neck/back troubles, I don't think you need it -- and if you do want the support, a stability ball should suffice, not to mention costing a lot less $$ and taking up less space (while giving you a greater variety of workouts.)
Current program: 1,800 calories most days of the week; 45-60 minutes of mixed exercises (weights, cardio-kickbox, dance, athletic intervals) 6 days a week
Current goal: 135 pounds by birthday (July 14th) and to run half marathon at end of May.