Okay, I’m giving Quicksilver another chance. Must be the fourth or fifth try.
I must admit, I’m not exactly the most patient user. If I don’t benefit from a program immediately, it can’t be any good. At all. And so far Quicksilver never jumped at me and said “Hey, this is why you should be using me!”. All I ever heard was other people saying how great Quicksilver is and that everybody should use it.
So far I got along pretty well with my combination of Spotlight and Overflow. But I have to say, at least Quicksilver is a lot faster at bringing up the files I want to use right now.
Anyway, I’ll just give it another try.

Addendum:
I’ve used Quicksilver since yesterday morning, almost non-stop. I have to say, I love it. I use the Flashlight interface, which formats Quicksilver to be a Spotlight-like field on the left side of the menu-bar. I’ve used Spotlight maybe two times in the last days, Quicksilver having completely become my application launcher. Hell, I don’t even use Overflow anymore.
What I have come to love most about Quicksilver is the web-search. I call Quicksilver, press “G”, tab twice and I can do a Google-search. On my desktop. Automatically calls Firefox and everything.
I love Quicksilver.
(Though it could be a bit more stable.)