Eric wrote a review of Gore Bike Wear Xenon GT AS Jacket on November 7, 2013
Familiarity: I've used it once or twice and have initial impressions
This "jacket" is probably misunderstood by a lot of people, but it is a valuable piece of fall/winter cycling kit in the right applications. It is early days for me, but so far I have used this jacket on a rainy ride at about 9 Celsius (48 F) and it kept my core dry, underneath I had on a SS base layer and LS jersey. Water seemed to bead up and roll off nicely and there was no leakage as the seams are taped. I also used in a cold dry ride where the starting temp was 2 Celsius (36 F), underneath was LS base layer and LS jersey. Kept the wind off nicely.
I bought this piece because one of my winter items that seems to get a lot of use is an old Sugoi Hydrolite jacket that I cut into a short-sleeve. In the Northwest where I live, a lot of days are of the "light rain all day" variety, and I find most full-sleeve rain jackets overheat me (even those made with eVent or other high-tech materials). The Xenon should substitute for the Sugoi hybrid nicely, although it is a little more bulky for a jersey pocket. There are no external pockets but there is a small internal chest pocket. I would always have a jersey under this anyway, so pockets are not an issue.
In terms of sizing, I am 6', 170 lbs and have a 38" chest. I went with L and the fit is OK, it is pretty snug across my chest if I sit up and reach back with my arms but in the riding position it is fine. I do find Gore sizing a little strange compared to Castelli/Giordana/Assos. If the item fits me in the chest, there is also a bit of excess material in the shoulders. My shoulders are very narrow though.