I think the OP is asking for general advice re. running a subscription-based web app, which Hacker Newsians are very well p[laced to do. Since he's light on specifics, I'll throw out some questions here which have occurred to me:

- How do you determine your feature/price plan(s). And if using multiple price plans, do you release all plans at the start? the most basic plan first? the middle plan first so you can introduce a higher or lower one?

- How do you manage subscriptions? Which provider? Is Paypal as good as place as anywhere to start? Can any of them handle voucher codes (e.g. 50% off for first 6 months subscription, etc)

- Do you offer a 30 day free trial? If so, do you require credit cards at signup for the trial? If you don't require credit cards, do you just lock the account until they upgrade? I guess the conversion rates have been discussed to death but you're probably looking at <5% conversion from free trial to subscription. Right?

- How do you handle cancellations? Pro-rate the monthly charge or not?

These are just a few thing off the top of my head which would be useful/interesting for others to share