Bought this on Joe D's advice (always great to work with). I've now used it at the coast from upper 30's with sprinkles and a 10+ MPH North wind, to the mountains in mid-40s with mist and drizzle, up to a clear mountain day that topped out in the mid-50s. These were 1.5 to 3 hour rides and the mountain rides included several Cat 2, 3 and 4 climbs.
As other riders have noted, the Alpha ROS is very versatile, with under layers key. At 5'10" and 170lbs I could wear a L, but the XL fits fine for winter workouts, allowing layering up with plenty of room, and layering down while still retaining a nice clean fit. The 3 back pockets are large and deep, and the front zippered cell phone pocket is perfect. If forced to list any down side, I would say the sleeves are just a tad long, the inner liner zipper is difficult (or impossible) to work with one hand while riding, and the Special Edition color is really cool but doesn't offer much in terms of high vis. Overall though these are minor issues.
As mentioned some of my test rides included significant climbs, with the corresponding cold (and fast) ride back down. Zipped up and popped on light gloves for the descent and the AROS kept me toasty.
I was worried I would overheat on a 3 hr mountain ride that got into the 50s but I didn't. I had a lightweight 3/4 zip under layer so I could left off some steam while climbing. It was still cool in the shade on north facing slopes, with a bit of snow left on side of the road, so the trade off between a little warm on the climbs and toasty in the shade and on descents was well worth it.
I've only had it in light rain so far, with no problems. And of course no below freezing temps yet. The AROS easily shed the rain I have been in, and I'm confident I can layer up for rides down to about 30. Much below that is below my lower overall temp tolerance anyway.
All in all the Alpha ROS is a great addition to my winter kit bag, especially at the Comp Cyclist Special Edition price. Thanks Joe for your expert advice!