For my part, I have the cheapest one they still sell here:
http://www.aiptek.com/Merchant2/merc...tegory_Code=T1
But if you're used to drawing on paper larger than 8.5x11 (and actually filling up the page), then you might want something a little larger.
They're inferior to Wacom tablets, in that they require an AA battery and have no functioning eraser. That said, I've only had to replace the battery twice or so, and I never much used the eraser on my old Wacom Graphire tablet anyways. (Personally, I prefered to use hot-keys to switch between eraser and pen tip when I had the Wacom. So, no skin off *my* nose, there.)
Those two things aside, it works absolutely the same as a Wacom tablet. And it has a thicker cord, which is what killed my Wacom. (The cord wore out and freyed about a millimeter out from the tablet.)