This is an outstanding jacket. When you first pick it up, it is so light you think there is no way it will keep you warm. That would be wrong. Part of the reason for that is the WindStopper.
This jacket is ideal for use in a three layer system. The perfect second layer to use with this jacket is a Marmot DriClime Windshirt. Vary your baselayer weight (silk, midweight, expedition) and you have a jacket good from 15 degrees on up. For even colder temps, add (or replace the DriClime) a Primaloft vest, such as the Patagonia Micro Puff. Stay away from fleece midlayers as they will not move as freely with the jacket.
This jacket does not have pit zips, but if you have the right midlayer on, this will be no problem. Just make sure your midlayer is very breathable (the DriClime is perfect for this) and the breathable underarm panels on the Superhero will do their job.
Also, this jacket is cut an inch longer in the back, which is nice.