I think the Valandre bags are very well made, but tried both the Mirage and the Shocking Blue and decided not to get them, for the following reason-- in the torso area it seemed that they were sized to allow one to wear a fairly thick down jacket without compressing the down in either the jacket or the bag. But without the jacket, it felt as if there were too much air in the bag, which would need to be warmed, and, as one moved during the night, would be a medium for carrying off heat whenever it puffed out of the bag.
YMMV, of course, but one should check the fit. In the same weight class as the Mirage, I prefer a NF Beeline I bought several years ago, which is cut narrower and hence warmer--and uses Pertex Quantum. It was also quite reasonable, bought in an outlet store.