The interface with the translation files is the best I've ever seen, and enables the user to customize the component from the admin. That's a very user-friendly feature.
Their custom development work is superb, and we've been very pleased with the Joomdonation component and every other component we've licensed.
EB allows the admin to create custom fields for the registration forms - a critical feature that makes this extension flexible and powerful.
A stroke of genius is an integrated editor for the language file -- enabling me to customize the screen prompts and labels without having to edit via FTP.
As an experienced Joomla! developer, evaluating many extensions every year, I have found this to be one of the best-coded extensions I have ever used. The developer has been very fast and responsive to inquiries. Support is superb!
In 10 minutes, I had accomplished what it had formerly taken me hours of template modifications to do (without having to modify the templates). The extension is well-documented and the recipes section of the web site includes code samples to cover any situation that should arise (especially the most common one I have – hide the left column navigation on the home page).