I have a montbell alpine light jacket, which is very compressible, has 4 ounces of 800 fill down, and has a total weight of 11.3 ounces. I have worn it alone to 30 degrees, down to about 15 with a very heavy baselayer under it. I think the flight is bit warmer as it has, I think, 6 ounces of 800+ fill, but is less compressible. I also have a down inner jacket, but that is not very warm.
The only problem I have had with the alpine light jacket is that it tends to get pretty damp in very rainy weather, but will dry out overnight. Also, the shell fabric is pretty thin, I but I imagine that the Thermawrap uses similar fabric. I am actually thinking about going the other way, maybe picking up a cocoon parka for fall in the rainy northwest, when I have the most problems with the alpine.