The Buddy line of heaters are propane fueled IR heaters. They heat you, not the air. IME they work ok, but they do emit some fumes, CO, and moisture. You need to have adequate ventilation which negates some of the heating capacity.
We've used a Lil Buddy heater on days where there is frost on the boat in the mornings. The heater got the job done, but there are better choices. However, the Lil Buddy can't be beat for the price. Since I only use it very occasionally, it beats the cost and maintenance of a real heater for my situation.
These heaters have built in O2 sensing and tilt sensors that cut off the burner. I've had it cut off when the boat was rocked by a wake from a passing boat. Having external CO detectors is probably a good idea. I certainly wouldn't leave one of these heater on while sleeping.