We've tried a number of rubber-tipped styluses now. Of all of them, the Pogo Sketch Pro distinguishes itself from the crowd.
The first thing you'll notice about the Sketch Pro is its long, tapered barrel. Designed with iPad artists in mind, it sits in the hand more like a paintbrush than a pen, and inspires smooth, sweeping movements across the screen (although it's equally capable of fine movement). It's also marginally heavier than other styluses, the effect of which is an implement that feels solid and elegant to manipulate.
Although the tip is wide, the stylus does allow a fine degree of precision. The trick is to not think about it too much: let your hand move naturally, and the rest will follow. You probably won't be able to do small handwriting, but if you're just scribbling down a few notes, that doesn't really matter: the great thing about a virtual notebook is that it doesn't use up physical pages.