A customer support and ticketing system is a must for freelancers and small businesses. Trellis is a free script and well designed and coded one I must say and is a perfect for small development shops.
In the past whenever I have tried to implement a customer support system it has been intimidating for me and my clients because it all seems complicated and we end up using the good old email for support. This is where trellis is a winner as it is has limited amount of functionality and very easy to use. The design is very elegant as well.
Give it a try if want your customers to be happy