I purchased this because I had a cookout in May, and the weather in the evening was still on the chilly side (50s or low 60s.  I have only used this heater that one time, but it seems to work fine.  I hope to use it more in the fall when it is cool outside.  I don't think it will keep anyone warm if the weather was in the 40's, however.  
The heater is slightly crooked when we put it together, but not enough for us to take it apart to see if we can straighten it out.