Well, I've been playing with it and testing it out ... I have apparently played 35 minutes today - at which point the game actually told me it would be a good idea to take a break - and they recommend 15-20 minutes for every hour played.
I am enjoying it. I have only the first 5 yoga poses available, but 2 are new to me (since I just started to do yoga not that long ago I have been sticking to very basic poses). The strength training is my downfall. Balance is the most fun and aerobic is fun too.
But I have one complaint ... when you are doing yoga or strength training - you have to do one exercise, go to the menu, pick the next one, do the next one, go back to the menu, etc, etc ... so just about when you feel like you are working, you get a break. I wish there was a way for you to string together the ones you want to do.
Also, I did the aerobic exercise (only 2 of them) and they don't last that much longer either. I can only hope that the exercises get longer as you unlock more of them.
Of course it says it was designed to be your only source of exercise and there is a way for you to go in and add the other minutes of exercise you have done outside of the Wii, so maybe that is why - this is just a method to learn the techniques, really work on balance and posture while doing them, and then take off with something that is harder? Who knows, I read that many think Nintendo is working on upgrades for the game already and :::Crossing fingers::: I hope that is one of the things they can add.
That said, I am having fun! I think the balance games are by far the most fun - the ski jump, well, I am rocking the ski jump actually LOL! I do not regret buying it at all and the kids want to play all the balance games too - so I think this could actually be a game that the whole family uses (when I really bought it thinking I would be the only one!)