I have this in an XS, I'm a 32C and it doesn't show anything. I wear this top all the time. It's perfect for climbing and yoga and anything active really. The only thing I slightly don't like about it, is that the flowing fabric at the bottom hangs a little strange. It's not exactly flattering---it's longer than I expected. But I love the top and it's so comfortable, I don't really care and wear it all the time anyway.
I'm not normally a 'dressy' person and stick to solids but this looked really nice after trying on. The straps are narrow but not tight. Love the longer length but that also means it looks better with capris or pants, not shorts or skirts. I usually wear a sports bra underneath since there's no support and this is probably good for the less-endowed. Overall, am really happy with this purchase.