Edit: As the market has evolved over the last few years and I've been exposed to a whole lot more in the way of lightweight, high-end technical clothing . . . I've reduced my rating of 5 to a 3.
This jacket is everything that Jay Ham's review says it is. It's pretty warm for its weight, the shell and liner fabrics feel nice, and eh, it's fairly light I suppose. The rub, really, is that a dedicated ultralighter can do a whole lot better. Having tried both now, I can say with fair certainty that this jacket doesn't compete with, say, Montbell Thermawrap stuff. To me it seems like the name of the piece should be Cirrus Light instead of Cirrus Ultralight. It's just not there yet.