I'm not sure about the added warmth (5 degrees?) for the thinlite, but it's a must have for me. It weighs nothing and as you said can be used in a frameless pack. Lay it out on the snow to keep things dry or double it up and you have a nice sit pad for around camp as well. My 2 cents.
Last edited by Uticafats; 01-20-2010 at 21:36..