In reply to minus273degrees:
I have a dreamcatcher 500, great bag. I wanted it for the stretchy panels in the legs as I get claustrophobic in the mummy ones. My wife got the helium 400, which is the same warmth, smaller and lighter (but a mummy) as she doesn't mind the confinement. I would say the helium has a better built quality as well, doesn't seem to lose feathers as much as mine does.
The coldest I have been out in mine was probably between -2 nd -5 camping in the deep snow last year in the Ochils (near Stirling), I was warm enough, but only just. Its great for year round use with the exception of full winter, which I find perfect as if it was warm enough for full winter, it would be too warm in summer.
Hope this helps.