Dave,
I don't own or have ever used a Northfire Inferno, but saw a demo of one at a store I went to a few weeks ago.
What initially struck me was that it appeared to be a well made unit but, at a weight of around 35 lbs. and dimensions of 16"X14"X10", it's kind of smallish which could be good or bad depending upon ones needs. It's definitely portable but lacks capacity. Also, with two temperature settings, Off/0°F or On/1500F, it's not very versatile. Finally, it did not have a timer with an automatic shutoff which could save your butt if you inadvertently got distracted for even a few seconds.
My final takeaway was that, at $500, it's a pretty expensive one-trick pony for occasional use under certain conditions. I passed.