I have an IR Ilumnator, made by SureFire, appx 4 years old. It's the older style not the current "M-1"(?IIIR), but I believe the specs are the same, the body just isn't as "artsy".
It has an IR LED that throws light like a SureFire visible LED. It is focused, fairly sharply, with a small amount of unfcused light on the periphery.
I'm not sure about range, but it needs a surface to "bounce" off of the effectively illminate. In other words if you aim it at the sky it is tough to tell it is on. If you aim it at a fixed object it will be real visible.
Mine was showing up pretty good last night in the woods, appx 40 yards away. I have AN-PVS-7B's. I think results will vary, cheaper night vision just doesn't work as well.
As far as IR illum. vs IR filter. Both will be visible to some people's naked eyes. I can see my illuminator when it is on. so have other people. But the IR filter is likely to have som white light escaping, making it more visible. It is less effiecient to create white light then filter it to IR, than to create IR light. Also Surefire lights run hot. If you put a filter over the bezel, it will run hotter still. You may damage your equip. or have the battieries thermal shutdowon activate, if you use the light in constant on mode. Not to mention the IR LED gets like 8-12 hrs of use out of 1 battery.