This is a the best method I have found for getting css image sprites working with both retina and non-retina images.

retina-sprite-recipe.scss

$sprites: sprite-map("icons/*.png", $spacing: 2px);
$sprites2x: sprite-map("icons-2x/*.png", $spacing: 2px);

@mixin icon-with-retina($name) {
  @include sprite-dimensions($sprites, $name);
  background-position: sprite-position($sprites, $name);

  @include hidpi(2.0) {
    $pos: sprite-position($sprites2x, $name);
    background-position: nth($pos, 1) / 2 nth($pos, 2) / 2;
    @include background-size(ceil(image-width(sprite-path($sprites2x)) / 2) auto);
  }
}

[class*="icon"] {
  background-image: inline-sprite($sprites);
  background-repeat: no-repeat;
  display: inline-block;

  @include hidpi(2.0) {
    background-image: inline-sprite($sprites2x);
  }
}

.icon-flickr       { @include icon-with-retina(flickr); }
.icon-dribbble     { @include icon-with-retina(dribbble); }
.icon-twitter      { @include icon-with-retina(twitter); }
.icon-pinterest    { @include icon-with-retina(pinterest); }
.icon-reblog-white { @include icon-with-retina(reblog-white); }
.icon-fancy        { @include icon-with-retina(fancy); }
.icon-reblog-grey  { @include icon-with-retina(reblog-grey); }
.icon-reblog-green { @include icon-with-retina(reblog-green); }
.icon-reblog-gloss { @include icon-with-retina(reblog-gloss); }
.icon-reblog-black { @include icon-with-retina(reblog-black); }
.icon-facebook     { @include icon-with-retina(facebook); }
.icon-eye-gloss    { @include icon-with-retina(eye-gloss); }
.icon-share-black  { @include icon-with-retina(share-black); }
.icon-heart-white  { @include icon-with-retina(heart-white); }
.icon-book         { @include icon-with-retina(book); }
.icon-tag-grey     { @include icon-with-retina(tag-grey); }
.icon-plane        { @include icon-with-retina(plane); }
.icon-home         { @include icon-with-retina(home); }
.icon-heart-red    { @include icon-with-retina(heart-red); }
.icon-heart-grey   { @include icon-with-retina(heart-grey); }
.icon-heart-gloss  { @include icon-with-retina(heart-gloss); }
.icon-heart-black  { @include icon-with-retina(heart-black); }
.icon-user         { @include icon-with-retina(user); }
.icon-close-black  { @include icon-with-retina(close-black); }