I ran up on a Sierra Designs Sandman +15 mummy bag this weekend. I've done some research and have read nothing but good reviews on this bag. REI's got it in clearance for $130 right now. Anyone have an experience with this brand or particular bag? Any comments welcome.
I have the Sierra Designs Forty-winks which is based on the same Flex system. Others on this forum are better qualified to give you a direct comparison regarding quality. I believe the Sierra Designs products are considered to be high middle of the road, meaning they are not as good as the Feathered Friends, Western Mountaineering level (top tier) but are better than the Coleman/Kelty brands. These are very broad generalizations.
That being said, I can address the Flex system. I believe it works well for me. It allows me to use a mummy bag even though I am slightly claustrophic. The bag stretches in the directions that I want to stretch but pulls up around next to me when I need to conserve heat. I do not do aggressive snow/cold/winter camping (bbbrrrrrrrr.) While the bag isn't "ultralight", it also isn't "heavy" and is easy (relatively) on the wallet.
Would I buy it again? Maybe. If I wasn't concerned with the clautrophic thing, I think I might have tried a more expensive but lighter down bag instead.