And here is why. Quicksort is quite famous for being O(n^2) worst case (for sorted data). Your straightforward, simple (and less generic, I must say) implementation shines for random data, but performs terribly for ordered data. Phobos' sort isn't really plain quicksort so it is slower for random data (yet still of the same complexity as your code best case), but it is pretty fast for ordered data.
Quite right! Phobos sort does a really good job with ordered data. The simple algorithm doesn't...
-Craig
