Piggybacking off RonJ66's comment...

For the D chord, I discovered that I wasn't pressing the high-E string down far enough because it HURTS!! So now I stop and really think about pressing that middle finger down. Now I've gone from being happy with the sound 1 in 10 times to closer to 7 in 10 times. 

I'm really looking forward to those calluses, haha!