I'm looking to get a capacitive stylus to use on my MacBook Pro's trackpad for quick sketches. This article by MacWorld and other reviews seem to indicate that the Griffin stylus and the Wacom Bamboo stylus are a couple of the best ones. But everyone is using these for iPads and iPhones... will they all work just as well on trackpads? The Pogo Sketch is the only one I see which is actually intended for trackpad use.
i use the wacom bamboo stylus on the ipad 2; probably the best stylus available. to answer your question, you will find that this drawing with the stylus onto the trackpad is impractical and will not yield desired results. in particular, the trackpad on the MBP (at least in the most recent generation) is not a high resolution input. more specifically, your drawings will turn out jagged and not as you would expect. you may be able to get away with editing documents tho, as this does not require precise input.
there are other caveats, such as the fact that the velocity of the pointer is proportional to the speed at which you move your finger (or stylus) across the trackpad; this can by a nuisance when trying to draw. you could purchase a bamboo tablet, which would be a more appropriate input device.