The Apple Blog has a great collection of Quicksilver reference videos that can help you get the most out of the application. Unfortunately, I still use it mainly as an application launcher (when I use it). I haven’t taken the time to really memorize all the key commands to do all of the wonderful things Quicksilver can do.
Speaking of application launchers, if you happen to be a Windows user, I think Launchy is probably one of the better launchers available.
I think as a rule, application launchers are much more useful for Windows than Mac. I think the Apple Dock makes launching programs much faster on a Mac than the Start Menu on a PC. There just seems to be more mousing necessary to use the Start Menu.
I suppose you could create a bunch of short cuts (or aliases) for your desktop on a PC if you used certain programs frequently. But regardless, you don’t need to do that with an application launcher.
For some reason, I still find myself using the Apple Dock more than Quicksilver to launch programs. It’s hard to beat one-click for speed. I find myself using Quicksilver most frequently when I need to launch applications that are not in my dock. I have around 25 apps in my dock and use about 20 of them each week. I could probably remove 3-4 of them, but I would find myself needing to use a launcher more often if I did that.
And like I said earlier, it’s hard to beat one click for speed.
Regardless of my launcher hang-ups, Quicksilver is still a great application.