My first reaction was to be delighted that there was something so (comparatively ;) ) short in the list :D. So of course, I read it straight away.
This felt very canon. Yeah, you tied it in overtly with the memories (excellent, classic HD moments), but the difference between the two relationships (H/G and H/D) felt very true to the development in the books. Heh. Right down to Ginny being the sweetly idealised one ;).
Yum for the violence, too. Nothing felt out of place here, too - nothing wasted. I'll admit that the length and the tastiness of this give me suspicions about the author, but I've always been crap at guessing :D.
If I could vote, you'd get full marks. I think this was really well done - an exploration of relationships over plot, and I'm an absolute sucker for the one-last-night scenario :).