My wife has the Flash pants, I have the Flight pants. Both are great and well made and seem to have a nice cut. I'm tall and was a little concerned about sizing, but no worries after they arrived. I purchased according to WM's size chart.
I think the Borah pants offer the most bang for the buck, especially when you start comparing fill weights.
All in all, down pants are really nice for hanging around camp or doing camp chores when the temps drop but probably less efficient as part of a sleeping setup compared to say, a properly rated quilt or bag. Definitely a plus in the versatility category though. From what you posted it sounds like they'll get you into the temp range you're after, the Borah's probably even more so.