When my heat is on full blast and coming through the windshield vents, I can definitely tell where it's coming from. When I have it towards my feet, it's a kind of that ambient feeling, like you said.
Either way, I can't have it on for longer than a few minutes at full blast, or I start melting. It does take a few minutes to warm up, but after it gets hot, it's nice 'n toasty.
I drove my 72 with headers from Atlanta to Nashville in January one year. It was below zero in the mountains. I had to alternate sitting on one hand and steering with the other. I forgot my gloves. Ambient heat? It could be worse, I s'pose.
