AFAIK it turns a laser into a mediocre frag cannon. A G5 mod introduces something like 5 degrees of jitter (wobble), so unless you're violating an anaconda you'll be lucky to land any shots.
Personally I wouldn't bother, though take that for what it is, I've never bothered, so I could be wrong. I think you'd be much better served by a corrosive multicannon for chewing hulls, or a cannon for sniping power plants. If you want a no-ammo solution (as I suspect you're after), I think it's all thermal or ammo, unfortunately.
Try looking up a Youtube vid of them in action, should be able to demonstrate their flaw pretty well.
Edit: You could always go a Railgun and role-play an NPC.
