Already had the Wii Fit game, but I am very happy with the upgrade. All game scores and data from the Wii Fit were transferred to the Plus game on first install.
There are some new features I really like:
1. approximate calories burned - so motivating! I am also now thinking twice about reaching for that biscuit!
2. 12 pre-set routines, approx. 5-10 minutes each. These can also be combined to fit time available.
3. Random yoga and muscle routines - you set the time (5 minute increments) and the Wii recommends a number of exercises to fit
4. easy access for favourites now sorted into three categories: frequently, recently and rarely.
5. it is now possible to access the balance tests already unlocked for practice outside the "body test". this is helping already with the wii fit age. There are some rather challenging exercises here.
There are some additional yoga and muscle exercises. No new aerobic and balance games compared with the wii fit (i would have really liked more step routines) but there are 12 additional mini games grouped under a new "Training Plus" menu. one of the other reviewers has already provided a list so I won't repeat it. I have only done a couple (love the Rhythm Kung-Fu), but it seems a good selection.