The Wii fails to deliver the fun to this game.
The original material from the Gamecube is unchanged fortunately; the power shots, the courts, the players, great graphics and additional camera positions were added. These additions I found nice, but the controls were the main problem. I extensively went over the demonstrations on how to do topspins, slices and lobs, only to get irritated at the ball doing the opposite that I wanted it to do.
As a result of the poor controls, it's a nightmare to enter tournaments. Sometimes you go up against CPUs who can't even play tennis, and then the next match you play a pro. The first two standard tournaments are simple, but as the CPUs get more difficult, you'll find you really need more precise controls in order to defeat them. It's not impossible to defeat the tougher CPUs, but it's excruciatingly difficult.
To summarize, all the Gamecube features are there, plus new camera positions. Graphics are fantastic, gameplay feels smooth and there is no lag. But once was a classic game loses its fun nature to unbalanced CPU difficulty in tournaments and horrific controls.