The IBM TrackPoint is by far the best integrated pointing device available for notebook computers. It completely blows away trackballs and touchpads (or, at least, the paltry miniaturized incarnations of the latter that are integrated into notebook computers). The absence of TrackPoints from Apple's notebook line may be the single most compelling reason not to get a PowerBook or iBook.
However, TrackPoints do have one minor deficiency: the caps wear out. After a little over two years of heavy use, my index finger had finally worn down the bristly coating on the last spare cap that came with my notebook. A little Googling led me to IBM's TrackPoint replacement page, which reveals that the traditional "Classic Dome" style --- shaped like a pencil eraser and coated with a bristly "cat's-tongue" texture --- is no longer the only option. (If you've drooled with envy over a colleague or friend's shiny new ThinkPad lately, then you've probably seen the "Soft Dome" variety, which I believe now ships standard on all ThinkPads.)
Anyway, the alleged "mechanical advantage" of the "Soft Rim" cap sounded cool to me, so I ordered a batch from IBM's suggested supplier. My report: Soft Rim TrackPoint caps rule. The cap really does feel more responsive because of the shape. Furthermore, the absence of textured coating has two benefits. First, there are no prickly bristles to irritate the pad of your finger. Second, Soft Rim caps don't have the Classic Dome's problem of wearing out their coating in less than a year of heavy use. This wear problem was the reason I had to replace the caps in the first place. Since the Soft Rim style uses shape instead of texture to provide finger traction, it seems likely that this cap will last significantly longer than the Classic Dome caps.
Now, if they only came in more colors... Apple, are you listening?