I've used this jacket a handful of time this past fall in temps ranging from 35-50 degrees F. The zipp off sleeves are a nice feature, however wind does seep through the overlapping layers. It is fairly wind resistant, but it is not at the level of a Windstopper garment. As for warmth, I tend to layer, so I can't say how this would feel with just a baselayer on. I bought an XL as I am 6 ft. 1 in. and 180 pounds. A large would fit a bit better and bee more aero, but the little extra room allows for the layers.