I definitely agree with "jmcquillan" in that if it didn't work it wouldn't still be here. Our Klondike was just this past weekend and two of my friends and I slept outside the night before at our station. The temperature dropped down to -25 degrees F (I'm from northern Minnesota, and no I'm not kidding :-) and we didn't really even build much of a shelter. It was a basic windbreak and we were all wearing wool pants (mind you, we are all under 21 so wool isn't just for Grandpa) and none of us got the least bit cold. Even if you are in an area that the snow is a bit wet, put a pair of fatigues over them. This prevents ice dams on your wool, and Fatigues won't melt.(They might get burn holes in them-like a scout shirt, but that's what they are for right?) Not only that, but as far as I have seen a good pair of wool pants are cheaper than a lot of the synthetics out there.
I say, go with the wool. Have a great Klondike!!!
