We (I run SlimTimer) went with a NYOP plan primarily because of we lack an obvious usage vector (ex: Projects) to limit and because it's hard to put a price on

We (I run SlimTimer) went with a NYOP plan primarily because of we lack an obvious usage vector (ex: Projects) to limit and because it's hard to put a price on something after you've given it away for over a year. A couple other implementation notes: * We don't prompt users to upgrade until they're a couple sessions into the service. Asking for them to name a price up front would probably result in a much lower conversion rate. * We don't give the users a blank box for price. Instead we compute a suggested price based on the number of hours they spend on the service. Overall, I would recommend stating a fixed price up front (and we'll probably convert to this once we build in the concept of a project) but the results thus far have been decent. The average monthly payment is a bit lower than I would have expected but the conversion rate from regular to paying users is a bit higher. I'm planning on doing a detailed write up of our findings on my blog in about a month or so. and I probably wouldn't recommend it to other people