I was an Alfred user for many months (since I've owned my Mac for just over a year, I measure application usage in months not years) before I decided to switch. I knew other launchers, such as Quicksilver, existed, and I had tried many of them, but none of them made as much sense to my mind as Alfred did. I had planned to stick with it. However, there were three things that led me to finally start using LaunchBar.

A couple of writers I admire, and trust (Shawn Blanc, and Ben Brooks) use LaunchBar, and seem to like it a lot. They even did a podcast episode about it.
While Alfred was remarkably faster than using the Dock, or Finder, I still felt like I was having to do a lot of typing to get stuff accomplished with it. Based on what I'd seen, LaunchBar just seemed quicker. To this day I have no idea if this is true or not, but LaunchBar still feels faster.
Currently Obdev (the developers behind LaunchBar) are bundling purchases of LaunchBar with the book Taking Control of LaunchBar. When I came across this, I wasn't originally even planning to purchase LaunchBar, but this book sealed the deal. It's been great so far. I figured out roughly 50% of LaunchBar's features, just by using it consistently. The other 50% I learned from the book. It's 100 pages of clearly written tips, and tricks.

I don't know how long the deal is going to last (it has been going on for a couple of months since the book was released). If you've even considered picking up LaunchBar, I recommend you get it soon. There are some great ways to extend its functionality. It's a solid application with some great history behind it, and a bright future ahead.