Sleeping bags are a very subjective thing - read reviews on any of them, and you'll see someone who thinks it's great, while someone else had a horrible cold sleepless night and thinks it's useless. So bear that in mind when asking for opinions about these things - some people are warm sleepers, while others are cold, do you know what you are?

I have the REI Travel Sack, and personally I find it very cold, next to useless in fact. I have not even tried it outside, but rather on the couch in the living room, and I found it to have almost zero loft, and felt cold on the skin. I was pretty cold all night long - and this was summertime here in Eureka CA (where, admittedly, it never gets all that warm, but not all that cold either). It didn't feel much different than draping a single sheet over myself. I like the concept of the Travel Sack, but it's not something I would take camping - for about the same weight you could do much better with something like the Marmot Hydrogen or Arroyo - both down bags rated to 30F, a really good option for summer touring.

Neil