I absolutely love this vest, and I am so glad that I bought it!My sister-in-law was raving about her Omni-heat ski jacket, so I wanted to try out the technology. I already have a waterproof ski jacket from North Face, so I decided to look for a vest version of the Omni-heat technology I prefer the mobility and comfort that a vest provides for most of the outdoor activities in which I engage. (I had a "Thinsulate" vest from LLBean that just wasn't working for me-- too bulky for comfort and not warm enough.)The Omni-heat vest performs exactly as I had hoped. I'm one of those people who is cold all of the time. I dress in layers wherever I go because I am never sure what the ambient temperature is going to be like. I have spent far too much time in my life huddled miserably somewhere shivering with cold-- people's houses, restaurants, grocery stores, you name it. I tried not to let my tendency toward cold affect my activities though. So I have been in constant search for jackets/coats/accessories that help me stay warm. I want to give you two examples of how the Omni-heat vest has proven itself to be a high quality product.First, over Christmas vacation, my family and I were on a ski vacation. My husband and I took our children snow tubing. On top of the mountain, it was 5 degrees, with a 20 mph wind and constant snow fall. I decided to replace the inner-liner of my North Face coat with the Omni-heat vest. Since the vest is so thin, it fit very comfortably under the coat-- way more comfortably, in fact, than the inner liner that came with the coat. I was out in the cold/wind/snow for 2 hours and my body was completely and comfortably warm. My hands and feet were numb, but my body was truly warm. It was amazing!Second, I live on the New Jersey coast. I routinely take walks along the boardwalk in the town where I live. There's always a wind. More often than not, it is a cold, south wind. With my North Face coat/liner, I would walk in the dead of winter, but always felt cold and uncomfortable. It got to the point at which I wouldn't even bother going for a walk if the wind were southerly and over 10 mph. A few weeks ago, I took a walk in the wind/freezing rain just to try out the Omni-heat technology. Amazingly, I stayed completely warm. My waterproof coat kept me dry, and the Omni-heat vest kept my totally warm.I'm being so detailed in my description for the other cold people out there. If you are a cold person, then you are going to be amazed at how effective the Omni-heat technology is at keeping you comfortable.As far as the fit of the vest goes, it works well for me. I am the type of person who likes clothes slightly large for comfort. I like to be able to move my limbs around without feelings of restriction. I am 5'5" tall and 120 pounds (fit and slender). I also am a 34D. I usually buy shirts and jackets in a Large to accommodate my bust (though a medium or small would fit the rest of my torso better). I absolutely hate the feeling of shirts or jackets compressing my bust. I bought the Omni-heat vest in a Large. As I had hoped, the Large vest fits comfortably over my bust, and it allows me to comfortably wear sweatshirts or bulky sweaters underneath. The only trouble is that it doesn't have the nice, "fitted" appearance of the vest modeled in the product photo. I like the extra space, and I am trying to stay warm rather than win fashion awards. The vest itself is very thin, and not bulky at all. The thinness of the vest does not detract at all from it's ability to keep you warm.In sum, the Omni-heat vest by Columbia meets my expectations perfectly. I got exactly what I was looking for when I purchased the vest-- a light, comfortable, high-quality vest that provides excellent protection from the cold. I recommend it whole-heartedly!