I have the 35mm DX, 50mm FX, and the 40mmDX Micro - here is my take on the ~$700 I've spent on these lenses.
1. 50mm I have not been as impressed with this lens. The 35mm nails the focus nearly every time, but the 50mm just doesn't seem as precise or accurate. Same camera, same person, same technique, results are just not as consistent on the 50mm.
2. 35mm, great lens! Super sharp and I have nothing negative to say.
3. 40mm is everything I loved about the 35mm DX and I can shoot macro photos.
My conclusion: If I could only have one of these lenses it would be the 40mm Micro. Eventually I would still pick up the 35mm. As for the 50mm I would skip it. I keep trying to find the love that I think should be there for the 50mm but I just can't seem to.
The lens produces a good sharp picture, but it has been in my experience inconsistent. The 35mm prime just can't seem to miss and always nails the shot. The 50mm I have to take a few and see if it focused where I told it to. This last picture took three attempts to get the focus where I kept telling the camera to focus. I've used this lens on both my D5100 and my D7100 and the only reason I keep it is if I want a prime with that extra reach. However, I know that I have to verify it did what I asked it to. It's a good lens but not a great lens IMO. I think it was Rocky that arrived at the same basic conclusion as I did if you want another opinion of the lens, but I know plenty that do love the lens.