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You don’t really need to purchase a tablet that is widescreen. With the right drivers, you can redefine an area on the tablet to correspond to the screen. It’s sort of like letterboxing the tablet area. Of course, some people think this is a waste of unused space, so I guess that’s why Wacom is making widescreen tablets now.

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Graphire is Wacom’s consumer line of tablets for the average user, while Intuos is Wacom’s professional line for the serious user. The main difference is that Intuos tablets offer more sensitivity (higher tablet resolution, more levels of pressure sensitivity, and pen tilt detection). With the Intuos 3, Intuos tablets now have ExpressKeys and Touch Strips on either side of the tablet area for convenient keyboard shortcuts and scrolling without switching back and forth between the keyboard and tablet.
Wacom also has a Cintiq brand, which integrates a tablet with an LCD screen, so you’re actually working directly on a screen.
I’m sort of surprised that you haven’t checked out Wacom’s website for this info… Or were you hoping for personal reviews of these products? There are quite a few Wacom tablet threads on CGTalk that can be easily found with the search function. 
- How you hold the pen is up to you. How the pen contacts the tablet is another matter. If you tend to write and draw with the side of the pencil point, then there might be a problem since Wacom pens work better if you write and draw with the tip. Basically, it’s more like using a ballpoint pen in that sense. I’d suggest finding a store or a friend with a tablet and trying the tablet before you purchase.
