I would reccomend against buying it solely for one game. There's lots of other good Wii games you could get. Then again, with the Wii U coming out soon, I have to question whether it's worth it or not. Some Wii games are really good, but many I've seen are, to be lbunt, kind of crappy.
As much as I liked Skyward Sword, I'd have to say no. There are other games I've played that I enjoyed much more than Skyward Sword and those games are the reason I bought a Wii. The games I did buy the Wii for was Super Smash Bros Brawl, Super Mario Galaxy and Metroid Prime 3.
I myself didn't purchase a Wii until after Skyward Sword was released. They are cheap enough now and SS is a great enough game that as a Zelda fan I can say it's worth it. Also there are quite a few other games on the system that look appealing enough that it's worth it.