I ended up returning this shirt for a couple reasons. First, the shelf bra & the gathered detailing don't line up at all. The detailing on the shirt hangs several inches lower than the actual bra inside, making my boobs look super saggy. The straps/sleeves felt quite long, too, making the top lay too far down on my chest. Also, the design of the arm holes is odd. You can't tell from this picture, but they are very large, and come around to the front of the shirt slightly. I felt like if I moved a certain way these generous arm holes may let a bit too much side-boob slip out.
I ordered an XS, which I usually wear for tank tops, but this shirt was far too tight, and the material had less flexibility than I expected. However, even though I had to struggle to get in & out of the shirt, the shelf bra was too roomy, so it wouldn't have fit any better in a Small.
For reference, I'm 5'2", about 115lbs, and wear a B cup.