Very short and very sweet. I would love a follow-on showing how(show spoiler)
Something about this story charms me. It is very short. It leaves lots of questions unanswered. It is pretty predictable.
But I just love it anyway. I love that Rodney is a gargoyle. I love how he copes with the limitations of his state (only alive at night, must hide, must be back at his perch by dawn). I love his little collection of belongings and the time he snuck in to see a play. The things he has figured out about people and life - and the things he hasn't figured out - are delightful. And his physical description is awesome (I have a real weakness for not-quite-humans).
David isn't as well described. I like him because Rodney likes him, but I don't know him that well. He does properly appreciate Rodney and doesn't freak out when he learns who he is, so he passes the important tests.