Your writing amuses me. I'm usually not a fan of third person, but this wasn't half bad. :) I enjoyed that fact that no two sentences sounded redundant or cliched. Your wording was clear and crisp and your plot was simple, but not the bland cliche it could have been.
You definitely had me up until the sex. I have to say, the emphasis on the mid-kiss transformation was one thing, but I feel like you could have emphasized that more to make the sex have higher impact. It seemed almost pointless to add that bit in there.
However, I have to say that I liked this. You did a good job of keeping the characters down to earth, realistic, and your simplicity was highly entertaining. Also, your words flowed very well. :) Nice job.