Beyond thrilled at the purchase of this jacket. For a year or so now I have been debating spending the extra money on a Gabba vs keep using the traditional $50 trashbag style rain/wind proof jackets. I finally caved and picked up a convertible Gabba. I take a size small in Castelli jerseys/bibs so I went with a medium for the jacket. Sleeve length is perfect and chest is not tight but still race fit to the waist.
High quality seams all over. Material is very durable and stretchy. Grippers on waist keep the jacket in place, never have to adjust. Wrists are not tight but have grips to keep them in place on skin or gloves. Collar is soft and actually does a good job at pulling sweat away. Nanoflex all over which does a good job to keep you dry up to a certain point. But let's be serious if you are riding 3-4hours in steady rain/snow and expect to stay bone dry that's just not realistic. This is very windproof but still breathes and pulls sweat away better than any jersey I've used. You could easily wear this jacket with no base layers into 50-65F+ and not overheat.
As for the guy saying how he returned it because of the sleeves are not removable while riding, well they make such a product and they are called arm warmers. Castelli designed the zippers on this jacket in such a way so that you can't feel them in your arm pits. If you have the sleeves on it feels like a normal jacket, sleeves off and its a regular jersey. No bulk. The best thing about the zippers is that with the sleeves on I can half zip the sleeves and get air flowing into the arms when I stop.
Overall, I will never second guess buying a Castelli product again. There's a reason so many pro tour teams have unbranded Gabba's, because they work a hundred times better than competitors. You pay for quality and functionality and it is worth every penny.