I spent 10 days last Sept. in Colorado and I would have packed it up by the third day had it not been for tents. I had a Hubba tent (freestanding, very well built, and you could pitch only the fly if you wanted) packed for spike camp, and I was soooooooo glad. We never did spike in, we were within striking range of the elk from base camp. We stayed at the base camp with a canvas tent and heat. It rained, snowed, or sleeted on us 9 out of 10 days ..... sometimes as many as five times in a day. I am not from the west, so maybe I'm not the best one to ask, BUT I COULD NOT HAVE FATHOMED THE THOUGHT OF SPENDING TIME IN A BIVY in the weather we experienced. Hunting hard for 10 days at 10,000+' is a chore by itself. You simply cannot afford to add extreme discomfort to the mix. At least this is my take on it.
Bugs were not an issue.
Oh, and get a footprint if it's offered