I don't buy the holier-than-thou rhetoric employed by Dalton, which also trivializes a lot of the complexities in running companies, but I think the value proposition is fairly clear - for nerds like us at least.
It's not enough to entice me to use the platform, because as nice as it is that the founders are profitable, the wider appeal to a general audience requires an electron microscope to find.
Besides having the API docs in Github I've never seen how it's much different from other companies that charge users.
Nontheless, I wish them luck because we need more self sustaining services on the web for consumers.
I'm sure it isn't easy for Twitter to make money, but their reputation is still in tatters, because of all they've done to affirm their position and guarantee what they believe is a healthy profit.
With most companies, we not only have to wonder how they earn or plan on earning money (Instagram! Quora! Facebook!); their business plan may not even suffice.
Tumblr is currently twisting and turning to monetize their platform more, because David Karp has refused to use a business model that is implemented at the expense of users. But good intentions don't guarantee a (sizeable) profit.