I would if I was very serious with the guy, and the city was somewhere I would want to live anyway (and one where I'd be able to find a good job!) I was with my ex-boyfriend for five and a half years. He lived in a teeny, tiny town about two hours from where I live. He did move up to this area for about a year but was pretty miserable...he's much happier living in a small town. Meanwhile, there was no way in hell I would move down there. There weren't really too many job prospects for me and we both knew I wouldn't be happy at all living there. Needless to say, the geographical issues was a big part of the reason we broke up. Had he lived somewhere like, say, New York City, I'd have moved in a heartbeat.
A friend of mine just moved down to Texas from Illinois to be with her boyfriend - well, now fiance! They'd been together for over a year and the plan was always for one or the other of them to move so they wouldn't have the distance issue. She was able to transfer within her company to a location down there with no problems. She's happy with her decision.