When you print on demand, your printing costs are twice as high per copy, but since there's no middleman, you make more as an author. Of course, it's impossible to distribute, so it doesn't really matter. It's only a good option if you really only intend to sell a few copies to friends and family.
It's just like the equity equation. Also, being published once makes it easier in the future should you desire to go that route, while self publishing does not.
The way I see it, a writer self-publishing is like a hacker building his own servers and running them from his basement.
It's moving to Amazon hopefully tomorrow, which is why I didn't link to it anywhere. I'll probably post it to reddit tomorrow at some time. Nonetheless: the book is very high-quality, if a bit glossy, and Lulu's store is a very effective one. There's a full preview, too.
If you want to publish something that is taken seriously by the publishing world, print on demand simply isn't an option at this point in time. There are a couple reasons why. Many people, myself included, find it annoying to read digitally-printed books because the ink tends to reflect light a lot more. Also, many distributors simply will not accept books that are print on demand. It's difficult to reach bookstores without distributors.