There aren't words to express how great I thought this was, but there are two bits I just have to comment on:
The disorientation Harry felt when first returning to human form was so believable and I loved the fact he couldn't change back because he didn't know what a Snidget looked like - this rang so true when thinking about those disasterous Occulemncy lessons, Harry needs to be told what to do in order to be able to do it.
Snape's acceptance of the Snidget nesting in his hair was just heartbreaking when he mused on whether he was that starved of companionship.