I just purchased a black AimTrak lightgun and received it yesterday (2 day shipping from London to the DC area!). Anyway, after setting it up, it seems to work fine when using the MA front end. I can select the game like usual and the the AimTrak works when the game loads (some games take a bit more tweaking the first time you load them up). I've tried the Exidy light gun games as well as Lethal Enforcers 1&2, T2, Alien3, the Operation Wolf series, and a few others. I am using MamePlus 152 if that matters.
My only issue so far is with Operation Wolf 3... I can't seem to get the gun sight down past the top 1/3rd of the screen. I need to look into this issue more as it's probably some simple fix.