If you do buy it, I highly suggest using some sort of mathematical thingy to compute your moving average each day, instead of simple weight (it just takes a few seconds, honest!).I'm debating with myself about whether to buy scales, but it's still kinda emotionally complicated.
It really helped me on the emotional side of things, since I can completely ignore the wild swings weight tends to have on its own, and keep my eyes on the fact that I'm actually, gradually, slowly improving. (It's a simple method I read in a book called Hacker's Diet, I can give more info if anybody's interested).