I agree with Jester, a set price gives your product, and by extension, the creator a set value. You're not just saying "This is worth X", you're saying "my time is worth X", "Me as a person is worth X". If people don't want to pay that, fine that's a risk you have to accept when pricing a product. But I dislike some of the language behind support for PWYW, it runs very close to "doing it for exposure", which is a complete and total load of words I can't use on this forum. Beyond that, people have more respect for what they MUST pay for, than what they choose to pay for, or don't pay for at all.
I value my time and effort. Effort expends resources that cost money. Time takes away from time I could be making money, or doing fun stuff. So if time costs money and effort costs money, then naturally I should be paid in wom...er...wrong anectdote... That is to say, I should be paid for my time, even if I'm doing it "because I want to".
If I ever upload anything I've created to the DMGs, it will have a price, even if a low one.