I have the long sleeved version of this dress and was super excited to try on the sleeveless version, but it just didn't work nearly as well. the armholes are huge and will definitely show quite a bit of bra. the black pattern was also nothing special. i like the mock turtleneck and the dress has a nice swingy feel - would consider getting it if it went on sale. 

i tried on the small and the extra small - didn't notice a difference between the two. i think i have on the xs in the photo.