Launch without paid plans or wait until payment is integrated?
cperciva: With Tarsnap, I got the basic functionality working and started inviting people into private beta testing while I wrote the money side of things.  Once I had the money side of things written, I told my beta testers that it was time to start paying (I had warned them from the start that at some point the free beta would turn into a paid beta), and about a month after that I opened up the beta to anyone who wanted to sign up.This worked pretty well for me; I can't say if it will work for anyone else, of course.