I use a 6x8 wacom tablet (http://www.wacom.com) and it works great. Not too big not too small. I've never had a problem with it in Softimage, it's especially useful in the paint module, for creating splines, and point manipulation.
I don't use it for everything in Softimage, mostly I use it in photoshop. IMHO, Working in photoshop with a mouse is like painting with a brick.
Hope this helps!
Ed Harriss, http://www.EdHarriss.com
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