I repeat, a paintbrush stylus is COMING SOON. In February, to be precise—and judging by their intro-video, Nomadbrush will be just the accessory design-mad iPad-owners need for precise brushstrokes when emulating David Hockney's work. [Mocoloco - Thanks, Kate!]
From reading comments about tablet devices, it seems that the issue of styluses (stylii?) is extremely polarizing. Either people completely hate them or they love having them. I loved having mine on my old phones simply because the touchscreens weren't as accurate and because the OS wasn't really great for the phone (Windows Mobile 6.1) but at this point I think the OSes and accuracy have evolved well enough to make living without a stylus easy for most applications. However, on some occasions, I still wish I had a stylus, particularly because my fat fingers block a lot of the screen.
Take the Android game Xconstruction (which I highly recommend) for instance where you have to build bridges (I know, I'm a nerd), your finger will often get in the way.