Check out this site http://www.backpackgeartest.org/reviews/ It has lots of good user reviews. Use the manufacture rating as a way of lining up bags within a manufature's line. Almost all the reviews a read suggest get a bag rated at least 10 colder than you intend use it in. Most manufactures say there rating is in a closed tent on top of an insulating pad. A light 45 degree bag might be great for a summer hike. It can be augmented with a fleece inner bag for about $30 which REI says that can add 10-20 degrees to the bag. You could also use an outer shell. The Wiggy's system uses a sleeping bag and an outer shell, but for a lot less money you could nest a inside a second bag.

Marcy