Update:
Well, least I know it can work....
Just had a great little game of 2 player Terminator 2, with 2 guns. Totally independant machinegun goodness, 1 gun in each paw....
I noticed when playing around with all the available drivers (Smog's Guncon, Acorn's WinGun, EMS's Gun2Mouse) that when I installed Smog's driver, a second device is installed - an HID compatible mouse. If I'd noticed this sooner, would have saved me loads of testing, as this is pretty much the requirement for 2 seperate mouse controllers in analogmame/advancemame in windows.
Anyway, using Smog's driver, and analogmame, I got it working. The problem is that its taken me 30 mins of messing around with the keyboard to get smog's driver happy. It seems to hate my system. Works in windows 1 second, then won't the next. I have the same issue with just 1 gun attached, so its not the guns(EDIT: its not the addition of the 2nd gun, I mean). Acorn's driver is perfect with 2 guns in windows for me, but does not present the system with a HID-mouse. Smog's has the mouse-goodness, but is all over the shop.
I've emailed smog to get some help hopefully. Anyone else tried it? (I'm talking 1 gun here). I can only get vaguely accurate controlling the cursor in windows, and every time I make a config change (*any* config change, no matter how minor) it looks to me like the whole driver is re-initiliased, and on my system sometimes its fine, sometimes its not. The problem is that it takes control of the mouse pointer and shoves it off screen (fighting with the system mouse) even when the guns are not pointed at the screen. When its like this it won't work in mame at all.
Anyway, thought I'd mention it - if I can find out the issue I have with smogs driver, I'll be able to play all lightgun games in mame as far as I can see. (NB - need to look into tracking in jurassic park, as that did not appear to be linear).