If it's under 1000 pieces or so, unsorted is fine. I enjoy looking for that one exclusive piece (and can I just add that I also build on carpet and don't see what the problem is with it?) in the huge pile when I'm building a set. The bags are usually sorted by piece size anyway (large pieces together, small greeblies together, etc).
Now, if it's a large set, I'd much rather have modular construction/presorted bags. Then it's like building three or four different sets, instead of dumping them all in one piece. But within those modules it's fine with me if it's unsorted.
I do understand the unsorted frustration, though. When I was younger and didn't have my loose lego sorted in tackle boxes, it was all in one big huge bin. Let me just say that it's a pain in the butt looking for that rare-colored 1x2 plate when you need it....re-building some sets used to take hours...