I have never really tried to see the nocturnal bug activity, a small side note though, I was in a Sams's Club the other day, and they have night vision binoculars for $129.84 not sure of the quality, most likely fist gen technology.
My neighbor bought a pair a few years ago (gadget freak) to watch the bobcats at dusk. I don't think he liked them, or he would haved raved about them.
I have a night vision monocle. It is really bad, maybe 1st generation night vision. It is from some old soviet bloc country, the directions are even in broken english. Probably the cheapest and most effective way would be to use the night vision feature on nearly any digital cam corder. Set up a tripod and focus onto a likely spot and then film, or watch on your screen. The tripod would be very useful as my monicle would "dance" all over the place. Ok for looking at deer and large mamals. Fish and flies would be rough.
Probably right about they would not be great for watching trout after dark, not enough detail. The new camcorders are amazing both in low light and magnification!