I love this layer. I have a longer torso and have problems with many other brands being too short. I am 6'1 190 lbs with a slim to athletic build. The large fits me perfect and the arm length is great. I realize this style of layer has longer arms for when you want to use the thumb holes, but I have long arms as well so it really helps. I tried on a similar piece by Mtn Hardware and torso and arms were too short for me.
This layer is well made and has a fairly slim fit, but not like a true under layer like Under Armor that tends to be really fitted. Its great for running as an outer layer and works great as an under layer for show shoeing, hiking, etc... The fabric has four way stretch and wicks as expected.
The only minor issue I have with this piece is the arm pocket. With the fabric being thin and stretchy it makes opening the arm pocket zipper with one hand a little difficult.