Thanks for all of the replies, guys. I've used the jacket twice now - yesterday and today. Temps were in the 50's yesterday and low 40's today (no wind to speak of). In the cooler conditions today, with a base layer of Russell Athletic Compression Mock, then a cotton T-shirt, then a cotton zip-up T-neck (I haven't gotten any non-cotton layers yet...) and the jacket on top, I was fine. A bit cool at first, but then comfy.

However, my hands (specifically fingertips) were quite cold. I wore these full-finger gloves under fingerless bike gloves. Not only were my fingertips cold but my hands (especially the left hand) cramped up pretty severely. It took soaking in warm water and 10 minutes of stretching the cramped muscle before it would finally release. Anyone have any recommendations to keep the hands warm (and hopefully un-cramped) in the future?

Thanks!