I bought it to wear in hot weather and it does stay cool. I haven't worn it as a base layer yet and that is probably where it will work best. Wearing it as a jersey is a bit strange since the pockets are arranged vertically up the center of the back and not across the lower back like a typical jersey. Also it is VERY long, if i stand to pedal and then sit back down on the saddle I end up sitting on the tail of the shirt. A real problem if you have something in the bottom pocket.....
I wanted something with long sleeves to wear during hot weather, the fabric is breathable but it's too long. If I stand up and on the pedals when I sit back down I'm on the tail of the shirt (and whatever I have in the pocket). It only has one useful pocket, the second pocket it between your shoulder blades (try reaching into that one!). I'll use it as a base layer when it get cooler but not for hot summer days.
Fantastic cooling capability. I bought the flag design, and got lots of compliments on it during a 75 mile event ride, which ended in temps over 95. It provides a great (sweat proof) solution to sun protection on long rides. I love the fit too - size medium (I'm 6.0 and 175lbs)... but runs long in the body, when I have loaded with phone and food in the vertical pockets it tends hang very low on the butt, touching the seat
As a cyclist I'm looking for lightweight layers for use under my short sleeved jerseys mostly to be used for the UV protection. I'm 6'0 and 178 lbs. the size is perfect. Gotta like the color as well! Priced a bit more than I'd usually pay, but overall I'm pleased.