Like Chris Bowler I am a major fan of Launchbar. I used Quicksilver in the past, but made the switch to Launchbar around the version 3 timeframe.
The thing about Quicksilver, Launchbar, Alfred and any of these launcher apps is that they are swiss army knifes for Mac power users. Despite all the functionality they contain, I use two features in Launchbar. The main one, of course, is the ability to quickly launch an app by typing Command-Space and typing the app name.
Beyond that? I absolutely adore the clipboard history feature. I never was a multiple clipboard app kind of person before Launchbar, but its ability to store my last 10 items on the clipboard has become so essential to my daily workflow that I couldn’t imagine using a Mac without it.
I use the clipboard history as a scratchpad of sorts when writing. I’ll stick paragraphs on there and come back and paste them into the finished later on. When I am refactoring in Xcode, I’ll often copy a chunk of code to the Launchbar clipboard so that I can paste it back in should I change my mind with the direction I am trying to take a code. It is poor man’s version control for those little development tasks.
I’m sure there are dozens of little features in Launchbar I would absolutely love and adore should I take the time to learn to embrace them, but launching apps and clipboard history have kept me occupied more than enough to justify the $35 license fee.