I use a Intuos 2 on the desktop and keep an older something-or-other (older littler blue/gray one) in my laptop bag. I use the tablet for almost all my regular Windows navigating/whatever as well as drawing in Photoshop or Illustrator.
Two comments on picking a model:
1. Price is dictated by size, but bigger is not necessarily better. My Intuos' drawing area is around 8x6, so my hand movements are no different than drawing on a piece of paper or in a small sketchbook, which is what i'm accustomed to. so it works really well for me. If you're a big sketchbook type of person, bigger might be better. If you're concerned about drawing little details, don't forget that you can just zoom in in PS/AI.
2. Price is dictated by sensitivity level. I *have* noticed some line quality differences on the cheaper models (both in recording the curve of a line and the thickness of the line). Maybe it's a lack of smoothness that's only visible when you zoom way in, but it's there and might affect your decision.
I've used a small Bamboo tablet, which I thought was completely useless. Bigger is definitely better. I have an extra large Intuos at my desk at work which is basically just a glorified mouse pad for me because I haven't been comfortable using it to draw. I can use the Pen Tool in Illustator no problem but haven't been able to master a wacom tablet--Go figure. Just make sure to go into system preferences on your mac and play with the Wacom tablet settings until it works to your liking. I find it more intuitive when I have "force proportions" ticked on
Getting the hang of a tablet takes a bit but I can easily say that when I got my first Intuos I cut my work time in have (after adjustment period). Then after buying the Cintiq I cut my work time in half again.
The new Intuos 4 is pretty rad and at $350 a real bargain. DD and Tom are right regarding tablet size. The 6x8 is a great size and the added wheel/dial is amazing with the CS4 canvas rotate.
I still can't design with my tablet though. They are perfect for drawing/painting but when it comes to layout and design I have to grab the mouse.
I'm in the same boat here. Can't decide between the Intuos4 medium or large!
depends on your drawing style. do you intend on large long strokes that will go across the entire screen? or will it be lots of smaller strokes. will you be zoomed way in to keep your eye on line control? remember that the tablet is going to be 1:1 with your monitor, so a smaller pad will translate a movement alot faster and longer than a larger pad will. the 9x12 is sort of perfect for me. but ive worked on smaller pads, but found myself sort of stuck in the size occasionally. the HUGE ones are sort of overkill. design office keeping up with the jonseses.