I've had one for a few years, a large summer weight sew through version. Bought when the exchange rate was favourable. Looking at the current prices I'm not sure I'd buy now, a decent quality rectangular sleeping bag would be almost as good, though they're not easy to find. On my own I use an airbed inside a sheet sleeping bag with the quilt just as a cover. For two we do something similar with two airbeds inside a single duvet cover. It's good for the sort of three season camping I do, once there's frost on the ground it needs something else, I just wear some clothing in bed. The airbed, sheet and quilt, makes it like being in bed at home so I always sleep well.
Before I got mine I was looking at a kit to make your own, they supplied everything needed you just did the cutting and stitching, it was around 30% cheaper, but I didn't want to risk it!