Exped have done a great job at setting the gold standard for down mats, but they do come at a weight penalty. Downmat 7 weights range from 780g for small through to 860 for the regular and 1180 for the 7 Pump DLX:
http://www.exped.com/exped/web/exped_homepage_na.nsf
Has anyone picked up a Kookabay mat ?
http://sectionhiker.com/kookabay-down-a ... irst-look/
If you're not familiar with them they are a US cottage manufacturer who do custom made mats, the link above details the weight savings which are quite significant. What grabbed me was the 3.5" (8.89cm) mat weighs in at about 520g for a mummy shaped down filled mat. So that is thicker than my downmat 7, still filled with down, and depending on the Downmat 7 you have, could be up to 600g lighter ! The only downside I see is the mummy shape - so it is smaller. This is similar dimensions to the Big Agnes mat I use and it's been fine for me.
Pricing is also competitive relative to the downmats.
I'm thinking it's a good way to cut weight and volume for winter camping.