Just pushed another update to JRFeedbackProvider on github. This update displays a "Thank you" sheet on successful submission of feedback. In addition, I added optional support for using the Growl framework.
To use Growl to display your thank you message, change
#define USE_GROWL 0 to
JRFeedbackController.h and add a new entry into your plist dictionary defining your other Growl messages. See here for more on using Growl.