Ultraviolet, infrared... bah humbug! I can't see either, so what's the difference? 

Yeah, that was the big difference for me too. Once it was explained to me how much radiant heat comes off the fire and is just wasted, I started making my fires a lot better. For instance, if I make a fire to heat up with, I put a great big log at the back to deflect heat back at the fire and at me. I also try to keep my burning logs above my fire ring (but below the top of the big log at the back) if I want heat. If I want to cook, or if it's hot out, I'll try to keep my logs below the top of the fire ring. 

When I really realized to potential of the radiated heat was the time me and some friends were at a really big bon fire (REALLY BIG, like >1/4 acre, and the pit was an unused quarry). we were at least 25-35 yards away from any actual burning wood, and we still all got too hot to stand there unless we had something to "shade" ourselves with. 