I generally wear a 10, but got the 12 for the length (I'm 5'10"). With 2 1/2 inch heels it was the perfect length. When I bought the dress I was a heavy 10, and was probably closer to an 8 at the wedding, but it is very forgiving looked great at all range of weights. It wore beautifully and was light and comfortable.
I had an extra snap added to the back, as the original wouldn't hold when I bent over. The dress is in perfect condition, with no stains or discoloration. I can send more photos upon request.