It works in MAME, I'm just having trouble getting a calibration I'm happy with. I'm always close, and always getting closer, to having a perfect calibration, just not quite there.
syph007: I set my aimtrak to device 3 in the aimtrak software. I set lightgun to lightgun in the mame.ini, then in the mame tab menu, I set the X and Y for the lightgun by moving the gun along the X and Y axis. I configured the trigger and other buttons by setting them as off-screen, so that in MAME, it doesn't freak out when you're moving the gun around as you pull the trigger, etc. Then I went back into the aimtrak software and set the trigger, etc back to what they should be.
Also, I only have a 19" CRT PC monitor, so I'm having to work with a smaller screen than most gun games use.