I've just pulled the trigger on an Osprey Kestrel 38 to replace my 45l pack. It's a bit aspirational, but hammocking in concert with efforts to lighten my load have definitely reduced my pack volume and I find the smaller size almost as nice as the reduced weight, just in terms of not having a huge carbuncle strapped to me when I'm trying to weave through the bush.
My goal for this year is to make myself a down top quilt to replace my sleeping bag.