The Gateway doesn't use the wacom digitizer. It uses a propietary digitizer that requires a battery to be in the pen, does not have an eraser, and has no pressure sensitivity at all. It lacks a lot of the usability and functionality of a real tablet, but it does have a nice screen. I would not recommend the Gateway at all as a tablet unless you are intending on using it mostly as a standard notebook. It is probably the worst tablet pc out there, in terms of tablet functionality. Price wise it is not that great either used as a normal notebook.
Toshiba M4 is a good tablet as well. 14" screen, 1400x1050 resultion, geforce 6600. I play BF2 with mostly high, some medium settings just fine @ 1024x768 resolution. Uses a lot of the latest tech, DDR2, SATA drive, etc.
A tablet's main use is for note taking that requires diagrams, artist work, or general input a mouse is inadequate for. A tablet pc's main advantage over the suggestion of buying a seperate wacom tablet is that you are drawing right on the screen, so do not have to translate what you are doing on the tablet to a screen feet away from your hand.
A tablet is not for most and if you are unsure if you want to make a jump to a slate type, get a convertable.