I have used Readability and love it. Reading on the screen can be tedious, and Readability definitely helps.
On the same topic, another tool that I like is http://www.instapaper.com/ . It's free and lets you bookmark pages for reading later. And like Readability, it just grabs the text and removes all the distractions, and makes reading on the computer pleasant. There's also an app for the iPhone/pod/pad. It's one of my most used apps.