I dated outside my race lots of times. Well the first time I dated a spanish guy but he was born and raised in the US so we didn't have too much of a culture difference. Just that his family spoke spanish. But I was friends with him for years before we started dating and at the time I was fluent in spanish so it was fine. It didn't work out because of him though. He was not a very good boyfriend. But I hear he's in a new relationship and he's treating her well so I'm happy to hear he grew up.
I dated this japanese guy and that was another good relationship but short because right when things picked up I moved to Korea.
So now i'm dating another Japanese guy and he's also great. I think i'm in love but it's a little too soon to tell. He even flew to Japan to visit me just for one day. He came, spend one day and left on the third day. And those were the best days of my life!
SO all in all I think most of it has to do with the people around you. Because the people in the relatioship oviously have no problems with race but their families might not agree and that can destroy a relationship.