This is so original and interesting! I love the complexity of their feelings for one another - their adultness. They seem to be meeting on equal ground for once, each with his (valid) reasons for wanting to be with the other.
I think I like the little details best - Harry at the cocktail party, blithely admiring the Indian ambassador's sari, Severus going a little weak in the knees over Harry's uniform. And, of course, teh hawt sex. Nicely done! :)