I was given this product by Backcountry, but this review is my personal opinion.

I use a lightweight, uninsulated GoreTex shell like this for skiing, both in-bounds (in warm and sunny Tahoe) and backcountry, and for bike commuting. The Optimizer jacket was a lot lighter than I expected and lighter than my boyfriend's or my old 2L GoreTex layer. It packed down really small in my pack when I was skinning and felt lightweight when I was wearing it. And of course, it is completely waterproof. I biked in the rain and stayed dry. I have only had it a few weeks and can't speak to durability very much, but it has seams where other jackets have tape, such as the pockets, and it is 3L, so I expect it to last for a while.

I am 5'5", 127 lbs and I'm a climber so my shoulders are a bit bigger and a lot of jackets are too tight there. The Optimizer fits well alone or over a fleece or lightweight down layer. It did not restrict my arm motion and more than should be expected from a well-fitting jacket. The hood has a cinch-pull so you can expand it if you're wearing a helmet or cinch it down if not. It fits over my bike and ski helmets, but is a bit tricky to adjust when the jacket is on.

The biggest downside to the Optimizer is that there are no underarm vents. The GoreTex is supposed to be "breathable" and I think it is a little more breathable than some GoreTex. Also, the front zipper zips up from the bottom so you can vent a little bit that way. I am guessing OR skipped the zippers to save weight, but personally I think they would have been worth it.