Under ideal conditions they are great. In non ideal conditions they are disappointing. We put one one a yacht I was working on eight years ago for the purpose of picking up pongas off Central America that would drift and sleep at night without any lights. Couldn't pick out any, earlier than the naked eye could. When the boat, water and air are very close to the same temperature you can't expect too much from it. Electronics technician in San Diego said the local tuna fleet put them on in order to see birds and were disappointed when they were unable to. In the northwest we were not able to pick up logs or crab pot buoys in the water until its almost too late because again it's temperature is the same as the water temp. No benefit found in fog or rain. Too much refraction from moisture in the air. The only benefit we found in open ocean cruising was that you could see the contour of the water. Inshore navigation is where it is most beneficial. A little more ambient light and temperature differential of objects makes them stand out a little more. I would still recommend having one if you have the budget and space for it. Any extra tool that may keep you safe and out of trouble is worth it. Just don't expect too much out of them. 90% of your night driving will still be done with naked eye, radar, binoculars, and chart plotter first.