I think it completely depends on your personality. I managed fine when my ex-boyfriend went to university and we were only seeing each other every two weeks. Well, I didn't manage 'fine', it was hard a lot of the time and at first I really hated it. But I made the most of what we had, and it gave me the opportunity to concentrate more on school stuff and seeing friends without having to worry about going to see him all the time, or worrying about whether I was seeing him enough because there wasn't any other way. However, I don't think he managed quite so well. Hence the now 'ex'. He needed a lot less space than I do, and needed a lot more contact, I'm probably more independent. Plus he changed at university, completely. His personality reverted back to how it had been before we had started going out, and it ended up that after a year of it all, he couldn't cope any more. Something wasn't right for him, and so it ended. I think his being at university though, rather than it just being a long distance relationship, may have had a lot to do with that. People change a lot at university, whereas if it's just you live on other sides of the country then you're less likely to do so. Maybe?
That said, I'd think twice about having a long-distance relationship again. Much as I was mostly OK with it, I did miss being able to go and have a hug whenever I felt sad, or if I just wanted to see him I couldn't just walk to his house to speak. Everything had to be planned, and when he was at home I had to be careful about what I did so I spent enough time with him. I didn't mind too much at the time, but ultimately you could say it was a bit of an inconvenience and something you don't have to think about if you're constantly together. Ultimately you've both got to be comfortable with the idea, and be independent people or it just won't work.
Internet relationships, I don't think I could do. I mean, I think everyone comes across so differently over MSN, even if just an extension of their personality (for example, I'm quite shy with new people in real life but I can chat away on MSN like anything. Quite sad really...). Plus the physical aspect of a relationship is important. I mean, fair enough if you meet someone over MSN, meet up with them a few times and then decide to get together and it evolves into a proper relationship from that- I know of people who are planning on marriage and have a kid after meeting on an Internet forum. But people who talk over MSN and phone each other every now and then, and who never really see each other, I don't think I could call that a relationship myself. Like I said, you're not necessarily getting to know the 'real' person, and you're missing out on the whole physical side which is one of the things which bridges the gap between best friend and boyfriend/girlfriend IMO.