The problem we've faced so far is catching buyers who want to solve this problem, the deeper, underlying issue, rather than the problem that's in front of their face.
For technical contributors, they're usually tasked to throw up a paywall, and you can do that quickly and easily using your billing engine and some lightweight hard-coded logic.
For the business stakeholders, they're usually paralyzed by an inability to decide what the pricing should be, and implementation is an engineering problem. I spoke to one buyer recently who was doing a re-pricing exercise (which Tier and Stage both promise to make easier going forward), but even he believed that this re-pricing would be the last, and that further adjustments would be minimal.
It's nice to see other, credible people enter the space - I think it actually is a problem worth solving, and it's neat to see how their approach rhymes with ours. Of course I don't wish them too much success, since I'd like to have some customers too.