Had a chance to try it last Saturday. It was interesting weather, mid 50s, intermittent rain and sun, sometimes quite windy. I wore with Rab Merino 120 base and Marmot Bantamweight WPB. Started out in light rain, about 20 minutes in sun came out and I shed the WPB. The Nitro was still warm enough, but once it was free of the shell I could feel how breathable it was. Sweat dissipated quickly, and just wore standalone rest of the way. At times it got cloudy and drizzled a bit, but the alpha shed that pretty easy. In terms of warmth and breathability it feels very similar to my Patagonia Capilene Air Crew. Both are very airy weave. Cap Crew is closer next to skin so strictly a base layer for me. I like the versatility of being able to wear Nitro alone or with a shell. Been warm here lately, plan to try with breathable wind jacket like BD Start or Kor Preshell this weekend.