Not sure if this question should be in hardware or applications - it occurs from a combination of the two.
In Firefox 3 and 3.5 on a Thinkpad (e.g., T61p) when the middle button is used for scrolling (see wiki) this problem happens:
The web page continues to scroll after the user stops pressing the trackpoint and middle button. I am calling this “overscrolling”. It means you “overshoot” your target and cannot easily use scrolling to navigate web pages.
On long web pages the problem is worse. As you are scrolling and you see the section you want to read, you release the middle button, but the page keeps scrolling way too far. So you try scrolling in the other direction and again the scrolling continues long after you release the Trackpoint.
The problem does not happen in other applications such as text editors. It is only in Firefox afaik.
Furthermore, the problem does not occur when Windows (XP, etc.) are run on the same hardware. This is a Linux-only problem.
For a guy who bought a Thinkpad just to get the Trackpoint, this problem is maddening.
EDIT: the problem is much less or non-existent with the touchpad afaik.