1) Just did. Also, mine is Ted Ritsick. I forgot to put it in the last post!
2) My favorite part of the app is definitely the twitter integration as far as features go, but personally the best thing about it in my opinion is the great content people have been able to put together by using it.
3) I love vine. I thought it was dumb when my friend with an iPhone showed me but the unique nature of it grew on me. The six seconds is one of those things where it challenges people to become incredibly creative with the short amount of time they have. So as far as the boundary goes, I would agree that it definitely does encourage creativity.
4) Andy Milonakis is by far my favorite, but if you're going to follow him fair warning there's some NSFW stuff so make sure you keep your volume down if you're at work or something. Mac Miller, Mackelmore and Caleb Shomo have some pretty good Vines too.
5) As far as Windows Phone exclusive features go, I know Rudy is working on a live tile, so once that's done I'm sure it will be excellent. One thing I would really like to see is lockscreen support, but since Vines are relatively low resolution, have the lock screen update to a pic-stitch style arrangement so that you can see multiple new posts on your feed right there.
Thanks for the questions!