Just about every piece of outer hunting clothes I wear and most of the underclothes as well is wool. Some of its plaid, some of it's solid colored, some of it's camo. I wear it for the warmth and quietness. Just about anything works sitting up against a tree or in a ground blind made of natural materials. Some of the lighter, more open camo patterns have the edge in open tree cover though.
Chuck: I've been wearing 18 ounce or lighter wool for years on my western hunts. Breathes real well and stays cool until the temps approach the 80s. At those temperatures, which I've experienced on a couple of hunts, I was hot even when stripped down to my skivvies.