I will preface my review with this: I have had some rough patches with JoomDonation. That being said, it perfectly matched my needs, and the customer service was impeccable. It's still a product that is maturing, gaining new features and squashing a bug here and there. But hey, that seems to be the case for 99.99% of all joomla apps. THe fact is that it helps process contributions through paypal and keep an organized record, all the while sorting the spammers out from view.
Whenever I have a question I can email the developer and/or post on the forum and got answers back right away. He even goes so far as to fix the problems himself if necessary. You don't get better service than that.
If you have a question, even before you buy the app, send the developer an email. He usually gets back to you within 24 hours with a response that is on target.
A- for the software
A++ for the service