The other point about Firefox GimpPrint etc is that the developers asked for pledges, but not for money up front. A pledge costs nothing until the product is available. So you cold not lose with Firefox/GimpPrint. Also, we had a good idea what we were going to get beforehand. The same is true of Messenger (I must get round to signing up for that, but I still haven't found time to install the latest Messenger Pro 3 upgrade).
Money up front though is a different matter. I won't pay for Iyonix Select until a) I see it working and b) I see something in it I consider to be worth the money.