there not as huge as the older system but they still take up a good protion of your pack and as will all issued dry sacks they suck you get about 6-12 months of use out of them then they pvc/vynil/ what ever they use for water proofing starts breaking away. I presonly have gone away from mummy style bags to a sleeping quilt from jacksrbetter (which is similar in theory to the mountian serape) for general 3 season but they require the use of a slepping mat for best insulation and there good down to the 20's (surival) but i wouldnt go to much below 40. The only time my mummy bag comes with me is snow camping and i only base camp in the snow, but hey i live in a desert currently.
also issued gortex just plain sucks i swear is the worst gortex produced i stopped wareing and using my issued gortex while station in japan even with typhoons rollng through its hot and dosnt breath very wirll and not very water proof/reseint. but thats my experance some people i know swear buy them.
almost forgot the bag it self is soild no big complaints there