Of all the styli for the iPad, the Jot Touch 4 seems to be the best as far as accuracy. It is the only one I'd put in the "usable" category." Surprisingly the newer Jot Touch Pixelpoint is horrible compared to this (missing strokes, not keeping straight lines, not being able to detect near the edges of the screen) and I wish I could return mine.

The Cintiq is a nearly natural pen and paper experience, but if I'm on the go, the Jot Touch 4 + AstroPad has worked out well.