It's incredibly easy to create support articles and manage support tickets, very user friendly for any outsiders and requires very minimal agent training as it's very simple to learn and manage!

Full disclosure: I'm comfortable hacking around with PHP and poking at a server so I may be a bit biased, but I have used this software since 1.x and I still install it for small businesses. It's free (after initial donation) , endlessly customizable, and just plain works. You can tailor it for so many industries, situations, and specs, without having to dream up bizarre workarounds like you do with most SAAS offerings. Even if you can't modify the code, it has a ton of built-in options out of the box... and that's how I use it for my own business.

The new version 3 Hesk has an amazing interface both on the front and back ends. Simple yet intuitive controls, decent amount of features and the ability to use either/or both the help desk or knowledgebase features. I love that you can run this on any local or web based server and completely customize this to your needs.