I've been struggling with this as well. I have a Bellweather Aqua-No jacket with pit zips and a rear vent, for wearing when it's really raining heavy. I could wear a jersey underneath it and it be 40 degrees out and still end up sweating heavily. When I wore it and it was dry out, I'd work up such a sweat inside the jacket that once I took it off, I could feel the sweat that had moved through the windproof/waterproof layer of the jacket because it wicks out and condenses on the outside of the jacket. Of course the inside of the jacket and whatever base layer I was wearing would be well and truly saturated. I recently purchased a softshell jacket on the recommendation of a friend who swears by his. He bought a Cloud Veil (?) jacket while mine was a Nashbar version. The softshell is okay in that I don't feel as if I get sweated up quite as much in it, but it still ends up reaching some kind of saturation point because near the end of my 40-50 minute commute I reach the tipping point from being warm and kinda sweaty to becoming slightly chilled and damp feeling. I've tried every combination of base layer and I just can't seem to get it right. I too wish there was something that would keep me comfortable and dry when the temps are ranging from 10's to 30's.