I'm not yet fully vegetarian but I'm currently transitioning (a week into it so far) and my boyfriend eats meat. Since I've been pescetarian on/off for a long time my boyfriend has always been aware that I feel strongly about animal rights issues and looking at/cooking with meat. He used to be a vegetarian himself a few years back so he isn't immune to these issues but had difficulty adjusting to a meat-free diet, so he reverted.
It's still early days but my boyfriend is very supportive of my desire to become fully vegetarian and is happy to eat veggie meals at weekends. Long term we may end up making separate meals if we move in together, at least if he wants to eat meat. We have only been together 8 months so we're getting to know each other in other ways too. I don't think this will be a major issue since he's very laid back and i take the philosophy that I can only change myself, no one else. From things I've said in conversation and his reaction I suspect this will cause him to reflect on his stance towards eating meat too, but I don't expect him to change to suit me.
We also differ on spiritual views so I guess it's another aspect of the same thing. We don't agree, but respect each other for how we each see the world. I wish I could talk to him about certain things but that's why I reach out for other support networks, What I do have in my boyfriend is a supportive caring companion (I see him as my 'Buddha lol) and that's what counts.
That said, if anything happened to him, I would most likely want to start a relationship with someone who is at least a pescetarian, preferably veggie or vegan.