I've got a 10k btu one i use in a single-car attached garage.
I got it because i live in a condo, and i can't install an outside-vented heater. I didn't want electric, because the electric rates in CT are astronomical, therefore i didn't have a lot of choice.
I bought it because a friend has one and likes it, and he reccomended it. I don't like it. actually, it kind of *****. Basically, all the problems everybody else mentioned. it stinks, and makes my eyes water, and throat sore after running it for a while I don't run it, unless it gets super-cold. In fact, i don't think i've run it for more than 4 or 5 hours total since i got it last year. I haven't even turned it on this year.