I joined as an atheist. But since being a member I've become a lot more knowledgeable. I've not lost any of the tolerance I had for religious folk, but I am a lot more educated on the kind of religious folk who do harm and I know how religious texts permit their abhorrent behaviour. I've learned a lot more about the bible too. Before my argument was that it was people just misinterpreting the bible and that actually the bible teachings good things, as Jesus seemed like a big huggable loveable hippy who people believe is a God and I believe may have lived, but died 2,000 years ago and lacked his super leprechaun powers people claim he has. But now I see that it's impossible to determined what a 'one true Christian' is. Nobody has got the secret decoder ring but they all believe they have and regardless of their belief the bible will have something that backs them up.
I've also learned how truly scary it can be living as an atheist over in the US, particularly the bible belt. And I've also learned more about some of the horrors Christians still do today, things I thought we had grown out of. I've also learned about Poes and realised how difficult it is to tell the difference from the real thing and how scary that is. It took me a while before I realised Baptists for Brown was not serious (there was the odd clue, for example, why would a raging bigoted Christian get an Eddie Izzard reference? Who is an outspoken atheist who was also a transvestite on stage). They were really persistent in defending their claims and being consistent, I guess I can applaud them for their effort.
I've also learned that angry atheists aren't as bad as people make them out to be and there's plenty of reason for them to be angry and I am now angry with them. And I learned how much people discriminate fellow atheists and it makes me appreciate that I've always lived with and been around people who don't really give a crap whether I'm an atheist or not. Had I been born elsewhere I might not have been so lucky, I may have had to keep my atheism a secret and pretend to dig this God guy.
[edit] Just submitted my 'other' vote. It's interesting to see where the votes went. Particularly the first one, I remember seeing someone claim that what we do here is pointless because we're never going to convince people. Though I do not remember the quote nor who said it - might have been the mailbag, I dunno.