We used Mantis bug tracker as support system. But this is heavy system with separate registration and logging in. It has a lot of over-features for user who just wants to report a sinple bug or ask a question. So we wanted some simple and user friendly way for users to report bugs or ask a questions on our site.
We had played with several third-party Drupal CMS modules and our new Support Ticketing System was born as result. Now you can leave you support requests (Support Tickets) at our site. You have to be registered user to be able to add a ticket. Use My Support Tickets link to add new ticket or view existing ones.
Our Mantis bug tracker is still available. But it will be used mostly internally by our developers. You can read about our custom Support Ticketing System building below.