Hm...This is probably going to sound like I'm just echoing what everyone else is saying, but do what you feel is right. Somebody said "if there's even a shadow of a doubt" then don't do it. I'd concur. Make sure you're absolutely, positively, 100% sure about this. Just put yourself in a hypothetical situation where something disastrous happened...could you see yourself being able to get through it with her?
And then again, this is the biggest decision of your life. I personally think it was a mistake coming here. For starters, it's a message board, and you can't detect sarcasm. And some of the guys on here are saying they'll never get married! I'm not saying there's anything wrong with that, but those aren't the guys you want to be getting advice from in a situation like this.
If you want real advice from here, IM or email the guys you respect here most. Ask for their honest opinion. If you really, truly feel that she is the one and you couldn't be any happier than you are with here, then go for it. But as people said, this is a lifelong commitment, and your life will never be the same...so I'd think this over long, and hard. As much as you possibly can. And then rinse and repeat. Do the process all over again.
And if you are sure and you end up doing it, congratulations, man. Glad you found the one...