If you have the money for one then do it.
The good thing about the Wii is that for the most part it can't really be compared to the other consoles because of the style of games catered for it.
Where the PS3 excels in racing simulators, Gran Turismo for example, brilliant game and totally suited to the PS controller.
The Wii on the other hand isn't about that style of game, a lot are simulators but in a differant kind of way. They involve the player in the game as much as you could possibly get involved. Wii Sports was a stroke of genius in my opinion and my first go of tennis had me giggling like a little kid! Games like Red Steel and Resident Evil show the serious side of the Wii controls and you'll ask yourself why you never played like this before! As well as Wii only designed games theres also a lot of titles that are available across all formats, so you also have the choice of wether you want to play conventionally or with the Wii controls, which really add to the experience.
The graphics are a lot better than people would have you think too.
Theres room for both in your life!