I have intially tried Huru helpdesk cos its free but the submission form is not customizable. Then I looked at other ticketing system in the category but decided to go with RsTickets Pro, since I bought Rsforms before.
I am indeed impressed with the complexity of the app yet very simple for me/my salespeople to understand and use!
Then I came to a template alignment problem with Firefox / Safari. A layman would put the blame on this product but since I am a technical person, its clear to me that this is a template compatibility problem.
The support team is willing to go beyond the normal scope and help me to troubleshoot the css problems in my template.
I definitely recommend this commercial product if your website is already up and running.