Here's a dissenting opinon on Quicksilver. I've heard so much good stuff about it, from such fanatical, um, fans, that I earnestly tried to love it myself, but I've recently turned it off for good. Too many cryptic options, not fast enough, and not smart enough (and I know, Quicksilver fans will now explain how with a mere option-command-f-splat and a flick of the wrist I can turn "OFF" the "SUCKS" option, and then by simply flipping a two-headed silver Quatloo in the air I can summon the "ADVANCED" DO NOT SUCK menu, but I can't be bothered to remember them, I just want to find my files).

I find Spotlight pretty useful, but it took a bit of customization and, I admit, of lowering expectations, to start to appreciate it. But of all the computer search thingies I've used over the years it is by far the best.