If you have wireless at home, that's good.
Depends on what you're using it for outside the network.
For example, you can text and surf the net on a iPod touch (and also make voice calls if you have a newer one), but you need a network for that.
If you have Angry Birds on it though, you can just play Angry Birds wherever -- you just won't be able to upload a new version until you're in a wireless network again.
The newer ones also have cameras and such.
We have an old iPod touch, no camera, it's very useful though. We got it for free with our iMac (special promotion, new iPods had come out), we weren't in the market for it or whatever but really appreciate having it.