I'm almost always a Medium or 10 in Sears clothing. I ordered this dress in a 10 and it is tight. The clingy polyester fabric makes matters even worse (particularly if that's not the look you're going for). Definitely size up (1 size if you're looking for something that just lightly hugs the body or 2 sizes if you're hoping or a more relaxed, loose fit). For reference, I'm 38DD, size 10. The neckline is cute and the pattern is vibrant.
The picture does not do this dress justice! The colors are so bright! The gold hardware around the neck is lightweight but is very comfortable. I bought it for job interviews, but just may wear it to a wedding I'm attending this weekend.