I concur - I love my primaloft gear, but primaloft is almost completely useless compressed.
for example, I have a lovely MEC primaloft pullover that is way lighter and more wind resistant than a fleece, and works great for that. but I don't take it if I'm expecting cold weather in a hammock because the fleece will keep me warm there, the primaloft compresses to nothing under me.

I could be wrong, but I'd compare them pretty hard against a plain old merino wool sock, perhaps with a good liner if you're so inclined.