I've been an atheist/anti-theist for two years, and I'm a lot happier now.
I'd like to point out that the poll makes an incorrect distinction between gnosticism and theism. Agnostic and Christian, or Agnostic and Atheist are not mutually exclusive. You can be both. In fact, most people are agnostics. Gnosticism only refers to whether or not you claim to know that God/Gods do or do not exist. Theism refers to whether or not you believe a god exists. Most people who practically consider themselves "Agnostic" can, in reality, be considered Atheists. An Atheist is simply someone who is not, overall, convinced that a God exists. If you doubt that a god exists (not have doubts, but think that it's improbable) or are unsure of a god's existence, then you are an atheist. An anti-theist is someone who actively holds the position that no (theistic/personal) gods exist.