I have now worn this windshirt running, mountain biking and backcountry skiing and it has performed better than I had dared hope in all three areas. It's light, has a reasonably athletic cut, a reliable zipper, a roomy hood and has been extremely effective as a wind-shirt not to mention doing a surprisingly good job of shedding light snow during two recent ski tours. To tell you the truth, I had assumed the Ion would do a good job of keeping the wind off but what had concerned me was its breathability. So far I could not be more pleased. it has stayed remarkably dry on several sweaty uphill runs, two uphill bike rides and a long ski climb on a windy but sunny day. Exactly what I had hoped for. I wish I'd picked another color (black is so -- well, drab) but otherwise a total score.