For someone who likes a little more comfort and looseness in their base layer, this is the way to go. For me, as someone who gets cold very easily, I need as little air between my base layer and skin as possible (obviously enough to breathe and wick away sweat) so this turned out to not be the best for me. Also, I got a medium that was way too loose but later tried on a small elsewhere and that fit much better, still loose but comfortable. For reference, I'm 135 lbs with around a 35 A/B chest.
"This shirt keeps you insulated pretty well!"
I have used this shirt for jogs in colder weather and during a camping trip in November. It definitely does the job keeping me insulated as a base layer. I ordered a size small and it fits a little more loosely than I would have liked it to (I am 5'2" and 110lbs). I just wish it kept me a little dryer, but maybe I just sweat a lot. Bottom line though, this shirt is a great base layer, fits a little loser so it's good for layering, and doesn't keep me as dry as I was hoping it would.
Arms that are long enough, long enough in the waste to stay tucked in... this is a super layer and keeps you cozy and warm. It doesn't create a stifling layer of warmth, so if you need to cool down, you can easily.
Although I love the Capilene 1 SW shirt, I find the Capilene 3 not so great. It has a somewhat boxy fit, and the texture is a bit stiff. I suppose that it does it's job at insulating, however I don't find this shirt to be flattering, well fitted and it doesn't feel great next to the skin. I would prefer merino wool for this type of shirt.
I wear this almost everyday for work (trail restoration in the Mojave Desert) and it's perfect for keeping you warm when you've got another layer over and cool when you're wearing it alone. It's a great basic shirt to have in your pack and I'd highly recommend investing in one.
I just took this for a run and I stayed warm and dry. Typically after a run I'm soaking wet, not so with this shirt. I can't wait to take it skiing. I'm 5'4" and about 125lbs and ordered an XS. Fits perfectly in the body, the arms are a little tight in the bicep area... just makes me look ripped or something.