It's quite difficult to elaborate in great detail, but I'd say it's not so much 'a better' life, as much as it's a different life.
For me personally it's been very difficult. I require a good amount of personal space to process thoughts. I causes friction at times. But even with my need for personal space, it's been working out just great.
Which is odd, as my partner and I are completely different. Where I like mellow and nice food, he likes heavy and spicy food. Where I like red, he likes blue. Where I'm calm, relaxed and controlled, he is assertive, driver and spontaneous. And the list goes on and on. They say opposites attract, but there have been major clashes before. I guess what makes it work is that we have small, but key, things in common, there's the absence of mindgames, and a strong trust to back it all up.
The bad has been REALLY bad,
The good has been REALLY good,
But most of the time it's mediocre. I don't know whether the factor of physical relations changes this, as I haven't had that yet, but for now the only thing I can say is that it's mostly just different. Not better, and not worse.
But that's just my personal experience, of course.