I have the Act-Labs GS Dual gun system and I think that the hardware itself is good. The software and drivers suck!!

If I knew C++ I would develope some new drivers).
First of all they should be able to run a TSR program that watches what resolution that is currently being used and store calibration presets for that resolution. Then the TSR program could bring up presets by watching what resolution is selected. Also a setup screen to calibrate each resolution and refresh rate could be used, once stored these values would make life easy.
I have a Thrustmaster joystick that allows the joystick configuration to be changed automatically by watching what game is running!

The drivers once written like this could run as point and click mouse shots, not requiring any MAME special code.
Currently the point and click setup requires you to pick a object on screen point and shoot at it, then move your mouse arrow to that location. This is fine if you don't move your mouse anymore? (how do you start your application, hotkey??)

Also once you do switch to a game that runs a different resolution your setup is f...ed! Bad setup!!
Now my advice is, until someone has truely tested this new gun, and I'm talking someone that has been around MAME for a while, stick with what you have!!
Hopefully Act-Labs sees this and is willing to donate a couple of guns to MAME testers.
Mat