I can only recommend this one too... I have to evaluate a new trouble ticket system last week. And of all the open source products I found this one was the best.
We had OTRS before. OTRS is very good too, but really hard to install.
A friend is using RT. Now with the newest version the user interface looks really good too. And I think many problems mentioned by others are gone.
I would recommend Avira AntiVir [1]. It is free for personal use too. The was most impressed of the speed. I used Avira AntiVir all the time before I moved to Linux.
Real Programmers don't eat quiche. They eat Twinkies and Szechwan food.