I've tried them, but they felt so clumsy to me that I don't see how I could ever be a convert. Trackpads, at least on Macs, feel precise and intuitive; I even use one on the desktop (unless I'm gaming).

I suppose a trackpoint might be useful if you really want your hands never to leave your keyboard, but generally I'm either editing text with emacs keybindings (where I don't have to use the mouse), or else I'm in a mode where having one hand off the keyboard doesn't feel at all hindering.

Maybe I could be convinced, but since they're hard to find these days and getting harder there wouldn't be much point (except to frustrate myself on the off chance I ended up loving them).