We have one and I really like it! I get on there a couple of times a week for about 20 minutes and it certainly does it's job.
I disagree with pp about the ab workout not being very good. It's a pilates style machine. If you engage your core and work on maintaining good posture in each exercise, EVERYTHING is an ab exercise! I've been using it consistently for the last month and my abs (and the rest of me) have noticeably toned :) I didn't need to lose weight, and my size isn't much different, but I look really good naked these days, if I do say so myself!
It isn't super easy to move around though. I do fold mine up between workouts usually (although it's been sitting all set up for three days now because SO said he was about to get on after me each time :-P) but you can't easily move it from place to place... I fold it and lean it against the wall next to the couch in the den. It's out of the way, but you can definitely see it there.