I've finally finished my sheet dress! It's New Look 6557. Not kidding, it's taken me since the end of May. It started out as version B, but then I tore out every seam I had stitched except the skirt side seams, fitted a new bodice piece from version E (to the top of which I added a 1/2" for extra modesty), and stitched it all back together again.
I'm beyond happy with the way this dress turned out. It's the perfect sundress: lightweight but not sheer, a gorgeous shade of blue, and it fits better than almost any other item of clothing I've ever worn. It inspires me to sew more. There are a few things I'd change about the dress. It's slightly too snug in the bodice (I took off too much when I took it in at the back seam...I should have left in an extra 1/2"), I'd change the neckline slightly so I could drop it lower but raise up the middle for a more subtle dip, and I'd add a little fabric in the arm holes so my bra doesn't show on the sides. The back doesn't match up perfectly at the zipper, but I'm not going to quibble about 2mm.
I wore the dress to a Labor Day party on Saturday, and I don't think I've ever gotten so many compliments on an article of clothing. I didn't get any photos of it on, but I will as soon as I can.
P.S. The whole time I was making this dress, I kept singing "Devil with the blue dress, blue dress, blue dress, devil with the blue dress on..." I think I'm going to start calling it the devil's blue dress. :)