Face it, if you buy a 5x4" tablet, your wrist will probably start to hurt after six months to a year of usage, especially if you use it improperly. On top of that, the small drawing area will make it difficult to create long lines the way you want them to.
Buy a Wacom. I've heard several stories where tablets of other brands have stopped to work in one way or another. Wacoms are durable, but they tend to come with a hefty price tag. Also, if you really can't get away from flipping the canvas when drawing normally on sheets of paper, you might want to look into buying a Cintiq. Cintiqs have built-in LCD screens that you can draw directly on, so you really see the image in relation. Very cool, but the downsides are the extremely hefty price, plus lack of pen tilting features.
The best tablet, in my opinion, is a Wacom Intuos (1, 2, 3), in the 6x8" or 9x12" range. I'm sure you could find unused ones on Ebay, but you'd still need to be willing to spend, say $300 to $400 usd to get a nice one. The retail price for a 9x12" Intuos 3 is $450 USD on
http://www.wacom.com
Nothing wrong with Graphires either. I haven't tried them myself, but I've heard they're like Intuos, with not much of a noticable difference in pressure levels (512 instead of 1024), but they lack pen tilting.
"Stephen Wolfram is the creator of Mathematica and is widely regarded as the most important innovator in scientific and technical computing today." - Stephen Wolfram