I don't want to give details too specific about who I want to reincarnate as, as it may be used to identify me, but, I definitely agree that I don't want to be human. Being human when you don't want to be human is one of the most miserable things I can possibly think of, because there's no real hope of fixing it besides death. Also presumably one might not want to be human because they don't like humans or interacting with them and would prefer interacting with non-humans. But in this world, the only beings we can communicate with in any intellectual capacity are other humans.
I just wish that people would leave us to end our lives in peace once they realized we simply want nothing more to do with them, or that our problems aren't realistically fixable.
Though I think it's very improbable that reincarnation isn't real, I don't see becoming non-existent as a bad thing. It's much better than the life I have now. But even though it may be foolish, I have a very vivid image of the life I would rather be living and I desperately hope that ending my life would somehow allow me to live that life. The people there would even be understanding to those who would want to end their lives and not resort to either physical force or banning of useful materials just to stop us.