So,

I just got the the mid-weight zip-t as a gift and have worn it a couple of times.  The fabric is very soft and I like the fit.  So far I have worn it as a sweater on a brisk day, I really have not had the chance to really test it out.  In a couple weeks I will have the chance to really test it in cold weather for more than a quick walk.  I will write in again once I really have given it a spin.

JD