I have an Army bivy I picked up on e-bay for about $150 with the two sleeping bags that come with it. I also bought a thermarest pad that fits inside. I've camped in Wyoming in November in it and was pretty comfortable. I've slept dry in a down pour in it too. My only complaint is that the head doesn't zip or velcro securely.

I just open the valve on the pad and roll the whole thing up and crush it in the compression sack. Takes about 10 minutes to setup and take down. I'll also carry a poncho or small tarp to protect my gear.