I've been using this for 2 weeks now, and can say it's a great substitute for a personal trainer. It really makes you ache.
The workouts are progressive in difficulty, but you are going to need a fair whack of space to play it in as you are jumping from side to side in a lot of the cardio activities.
My only gripe with it is that sometime it says you are out of rhythm when you are totally in synch with the onscreen trainer, this just leads to a bit of frustration especially when it affects your total workout score.
But it's got me back into keeping fit and I look forward to doing it every day. 4/5