Most all of my knowledge comes from USGI issue stuff.

I have noticed most of the non-issue stuff is Russian, so make sure it will use standard batteries. Would not be much fun to have some insane battery size you can only purchase on-line from the former USSR stockpiles.

Try to get something that has a protection circuit for exposure to light. Nothing worse than someone turning on a light unexpectedly and blinding you. (Not to mention damage to the NV device.)

Work on your neck muscles and flexibility. The FOV on these things is VERY limited. You will be turning your head constantly. Also depth perception is seriously degraded. Don't walk into any trees, and really don't drive in it until you are adjusted (and kill the dash lights).