TTimo of id Software recently wrote a new mouse acceleration scheme. The old q3 mouse accel, which is also present in ezquake, has a few drawbacks. No matter what value it's set to, the accel curve is always a square (power of 2), and the accel is related to more than just the sensitivity and dpi - even at sensitivity 0 the q3 (and qw) mouse accel will still move your mouse around. The new code is gpl'd, feels very smooth, and I think it should be in ezquake.
Here's the code,
http://github.com/TTimo/iourt/commit/8e361aeec0fc717e4c438824e5717eef8dd4a73e
and here's TTimo's explanation of what it does
http://github.com/TTimo/iourt/blob/8e361aeec0fc717e4c438824e5717eef8dd4a73e/ql-mouse-accel.txt
Funny no one have seen this one before, I've put it in the TODO list for 3.0