We use one. No problems so far. you gotta leave a vent cracked open just in case. They do produce allot of extra water vapor inside, but nothing thats a big deal. A bottle will run almost six to eight hours on low and four to five hours on high.
We have a 23 foot trailer and Low will keep us snug at freezing and above, have been in below freezing, but nothing below 30 degrees and the Mr Buddy works great for us!
With that being said,,it is a open flame heater and we do NOT go to sleep with it running, we use it to take the chill out and run the furnace when sleeping.