I had never worn base layers except in cold weather, but after seeing many pros wear mesh base layers in hot weather, I decided to give this a try.
I wish I had tried these a long time ago. Using one under bibshorts is much more comfortable - no more chafing from the straps, cooler in hot weather (as long as you're not wearing a tight black jersey), and warmer in cool weather.
I now own several of these and they've survived many dozens of washes with no adverse effects.
I was always skeptical about wearing more layers to stay cooler in the heat. But, I suspended that impression to give this a try. My conclusion It's still hotter when you wear more on hot days. Where this thing excels is when I do a mountain ride with significant altitude gain and rapid temperature change. It can start out hot and humid and turn cold and wet within a few miles. Having the additional layer in those conditions is welcome as it does help insulate the core. As far as the idea of a 'loft layer' that allows better air circulation between your skin and your jersey so that you stay cooler? I don't really think so. Get this and wear it if you're going on a long ride in changing conditions, especially if it's likely to cool down significantly over the course of your ride.
It's still too early to tell if this will fall apart over time. I plan on using it weekly as I did with my Pearl Izumi baselayer and so far it's lasted me 3 years with no issues. So I will compare it to my PI. It's very light, and comfy, keeps me cool in the Florida hot and humid weather. I don't feel sticky at the end of my rides and still able to not feel overheated. I bought a size medium, which I usually wear, but appears to be more loose. Maybe next time I'll order a small and see if it'll fit well. Anyway, like I said earlier my review might change over time since I'm going to compare it to my PI that I've been using for over 3 years and so far nothing wrong with it.
Used under jersey in all weather conditions. Keeps a layer of ventilation when it's hot out allowing cooler air layer between skin and jersey, jersey doesn't stick to the skin.