It all depends on what you're looking for, I don't know much about the new models, I bought mine in 2005 so I'm sure there's been a number of advances since.
When I bought mine, my main concern was workspace, you can get cheap ones but the working area is like 3" x " or something and it wasn't much, I got one that's about 6" x 4", it was still fairly affordable but much more work space.
For anything drawing, I'd recommend getting one with a larger work area. Even with the size of mine, I still have to move the image around on screen to line up w here I want my pen to fall, I'm on a 1920 x 1200 resolution monitor and the Wacom covers about 1/4 of the screen space.