Like andrewc, I'm currently using a Ajungilak one. The valve isn't brilliant, but if you shove it back inside and zip it up, that seems to stop it popping open.
I find it reasonably comfortable, and it has a nice fluffy finish. When I've used stuff sacs with clothes in, in the past, they tended to be too shiny, and I find my head has a tendency to slip off, or the stuff sac slides out from under me, iyswim.