I heartily second this. I've been using Thinkpads (T-series) for the past 10 years. The trackpoint is great -- you can navigate quickly and precisely while keeping your hands on the keyboard. No batteries, wires, or desk space needed.
It sits in the center of the keyboard, between the G, H, and B keys, where you can reach it with either index finger. That puts your thumb right over the mouse buttons that are under the spacebar.
They corrected some early kinks with resistance and calibration, and the trackpoints work about perfectly now.
It's true that for mouse-heavy activities, like drawing or editing graphics, it still feels a bit more fluid to use a real mouse or a tablet -- I have a lovely Graphire-4 tablet with a pressure-sensitive pen. But I never seem to use them, because almost everything I do needs the keyboard too, and the context-switch slows me down too much compared to the trackpoint.