It's just a tennis game with the Mario universe rules and effects, nothing more or less. The single player mode gets boring quick so unless you plan to play it online I wouldn't recommend getting it. Online play is competitive which is good but your opponents are unforgiving so play it a bit offline to understand the game a bit more. I recommend checking out a guide to know when to use the different kinds of shots because the in game tutorial doesn't help.
Ok, first lets start with the Pro's.
Amazing 3D graphics. Great customization. The multiplayer function is great, EZ to get coins, awesome tennis power hits.
Story mode, completed it in A DAY (I played the game 3 times, and I won 1st place.) Tournament mode, was completed in a day!!! Wayy too short. Sure you can replay, but the first time round, is supposed to take at least a week!!! In my opinion...
Also,the camera moving is SOOOO annoying. I can never get it to stay in one spot :(
Other than that, its pretty good. On a rating of 1-10, I give it a 7.5