I use the Wacom 9x12 Intuos. The 9x12 aspect ratio comes close to matching the layout of my side-by-side Apple 23" Cinema display. This model is a bit pricey but has worked well for me.
As for getting the hang of it... I had a terrible time. I tried to change over several times over the past 3-4 years. Each time was so frustrating getting use to the eye-hand coordination thing. So bad that I would sell off the graphics tablet, then try it again a year down the road, only to get frustrated again. Finally, when I switched my post processing from PC to a Mac, the Mac mouse was so clunky to use that the quality of my work went down hill. I made up my mind to basically put away the mouse and ONLY use the pen for everything on the Mac. That worked.
Now I don't feel comfortable with the mouse anymore as it feels way to restrictive. I have so much more control with the pen and I feel that my work moves along at a faster clip.
Oh, the type of pad was extremely important to me. I had a lower end model and the texture/surface of the pad + the type of stylus was just too slippery. It was like there was almost no tactile feel of the tip on the surface of the pad. I moved up to the new Intuos 9x12 and the tactile feel was incredible, almost like I was drawing on a piece of paper... perfect for me.
Just me two cents. :-)