It's very hard--but it can work. The best advice I can give is to know it's over when it's over (if that happens): I spent a long time in a horrible relationship that I knew was over halfway through, but I drug it out because I convinced myself things would be better or different once we met in person. While sex is a great way to relieve minor squabbles, the reality is, if you're fighting every day online or on the phone... "In-Person" isn't going to change that. It's hard, but it's important to remember.
My current relationship is a year and a half going VERY strong and we're going to be moving in together in... 12 days!
I'm thrilled beyond all belief and so ready.