Wow! *is blown away* I really think you did a masterful job with this one. I adore Firefly and I love how you connected the two fandoms, which is not an easy task.
The plot was well done, I was sucked in immediately, and when the final plan became clear I think I actually gasped. Fabulous job!
Mal was perfectly IC, as was Jayne ( I chortled at his continued and clueless flirting with Harry). HArry ad Severus were lovely. The relationship you assigned to Severus and Mal made a lot of sense, too, given both their personalities and the last "battle" was awesome. *is trying hard not to give the whole thing away*
I'll be honest, I don't read a lot of FF fic just because the show was so awesome, but this really makes me want to search for more (not that I have time, lol).
Anyway, you did a great job with this. Congratulations! :)