One interesting observation:
Of the 500 or so developers who are participating in the program, the average contribution falls somewhere between $5 and $6, with the largest thus far being $150.
Assuming there has only been one $150 donation, that is one I received for the CCK Wizard. To be fair, though, that person has been trying to give me money for the CCK for years, and as soon as they had the opportunity, they took it. That's the only contribution I've received for the CCK Wizard.
I'm still optimistic that someone will figure out how to monetize Firefox addons well. Maybe that's a good topic for the upcoming Addoncon.