Josh,
I have the double tin cloth pants. I've used them a lot in Alaska and the Yukon. Also winters in Arizona. They are incredibly durable and resist everything from moisture to those nasty catclaw thornbushes. They are baggy enough to get reasonable air circulation over your legs but will be a little hotter in tighter areas (waist, crotch, etc.). They are definitely not breathable, but I've never found anything that's really waterproof to be very breathable. By the time they get done making those high-tech parkas out of 2-3 layer Goretex, they're not very breathable either. Even my old single layer Goretex jacket wasn't particularly breathable.
I'm moving to Alaska and have been considering the Packer coat for that environment. Up there, you're sometimes betting your survival on the durability of your gear. I like the double arms and shoulders for ruggedness. I've worn the coat briefly at a few outdoor shows and feel that unless you cinch the bottom for warmth retention, there is a reasonable amount of air circulation for average walking. However, if I were hauling a heavy pack or cross-country skiing at a hard pace, I believe that the moisture generated by my body would exceed the evaporation facilitated by the modest air circulation.
The tin cloth definitely has a different feel and smell, as you know from your hat. I don't think that would be a problem for my intended application. However, I haven't bought one yet because the amount of time I presently spend in harsh winter conditions just hasn't justified it.