http://news.ycombinator.com/item?id=1538731
If Ars is doing a review of your beta, you should certainly be able to convince yourself there is a MVP in your hands. Why the perpetual private beta? Wouldn't you rather find out if this is something lots of people want and would be willing to pay for?
I would worry you finally ship the thing and realize that you need to tailor it to a different audience. Or perhaps the folk are willing to pay are rather happy with Dropbox and a centralized model.