The Next Best Alternative to using Pretty Graph would be using Excel, for most people. How much better is Pretty Graph? Better enough to convince people to "pay" the extra cost (of using something new, via a web interface, rather than something they're familiar with running quickly on their computer, probably in the same place as their data sits)?

I'd suggest thinking about how Prezi came up with an offering that is sufficiently much better than Powerpoint to persuade some people to make the switch (or at least give it a try). What about animated graphs, a la Hans Rosling (see TED talks).