I agree that they can work out, though they're very complex. I'm currently in a LDR, with my partner being in the UK, and me in the US. We're lucky because I get to travel to see him every 6 months. I can't say how successful we'll be in the future, it hasn't happened yet, but so far we're okay. Though... I just saw him for two weeks in June/July, and I have been itching to see him again since I returned home.
One thing I'll say is, immigration (even just on a tourist visa) can be a real bitch if you're visiting a partner. Saying you're just there for a holiday usually works for the first or second visit, but then immigration officials tend to get a bit suspicious. If you go to visit her, or if she comes to visit you -- either way -- just make sure that whoever is doing the traveling has documents (something verifying employment, a copy of your lease, etc...) on them to prove that they're returning to their home country after the trip. Having documents on me would've saved me 4 hours in secondary inspection on my very first trip to see my guy.