The component is nice and very useful but it contains some bugs. The bugs are excluding some components/modules/thems/plugins in the list because the J!Credits component is looking for an xml-file with a defined name, in case of an component the name of the component, and if this xml-file is not found the component will not be shown on the credits list. I have allready fixed this bug and mailed the corrected version to the author.
But all in all J!Credits is a component I can recommend it all users of Joomla. And the best of all is that it's free :-)

best regards Daniel Janesch