Originally Posted By bob13bob
if you you're youngish and don't mind the weight for hte miles walked, you don't need to spend money on a down bag. Like others said, sleeping bag ratings are usually liars unless you see two ratings, comfort rating and standard rating. I usually backpack in places that hit 40 at night, and I just bring my non down bag. I don't mind the extra weight, i'm in pretty good shape. A person in good shape with heavy ass gear will outhike and okay shape person with light expensive gear

I don't think this advice would work for me. I sleep very cold. I use a an REI Radiant (comfort rating 32, lower limit 19), and I'm comfortable in that bag probably between 50-60. Everyone's different, so YMMV.
The journey is more important than the destination.