Carbon Copy Cloner, my favorite bit of donationware, is so useful to me (and has saved my bacon so many times) that I send the developer a donation each time it gets me out of a jam.
I don't think that donationware is really a very good business model, honestly. Much as I hate to say it, I think that the best course for developers to take is to release software with some features disabled, and then enable them for registered (eg, paying) users.
