OS Ticket has been great for our organization in solving an issue we had with tickets not working as intended at one of our companies customers sites using their service.
The product team was very responsive to any feedback that I or anyone else gave them when it came time for us all to update from 3.0.2 to 4.3 which solved many issues regarding bugs etc but also added features such as mobile/responsive design (very important) allowing users access regardless if they are accessing through smartphone browser vs PC desktop. We have still some minor problems here & there like emails getting blocked by certain mail providers due to spam filter settings - not sure how this could be fixed however once again the product management staff were quick to respond to those requests by me directly so maybe just need more people looking out! Our main concern before switching over was security concerns given most businesses use third party services where you don't know what information.