Simple solution: Optional payment. Keep the promise of a free upgrade, but add the option to pay anyways if someone really likes it (if the current TextMate is any indication, many will).
I wish all software was sold like this: You get the full version for free, no restrictions, no nagging (perhaps a reminder once a month). If you really like it, you get the option to (easily, avoiding PayPal) pay for it. Heck, you might even let people choose the price.
Of course this would work only for software that makes people think: "Hey, someone really spent a lot of effort into making just the right tool for the job". Microsoft Office might not benefit from this method of "voting with your money" - but then that would probably be a good thing too.
I wish all software was sold like this: You get the full version for free, no restrictions, no nagging (perhaps a reminder once a month). If you really like it, you get the option to (easily, avoiding PayPal) pay for it. Heck, you might even let people choose the price.
Of course this would work only for software that makes people think: "Hey, someone really spent a lot of effort into making just the right tool for the job". Microsoft Office might not benefit from this method of "voting with your money" - but then that would probably be a good thing too.