Quicksilver build 5300 doesn’t play well with Leopard. The icon stays in the dock and in the tabbed-through-apps list. Also the auto update doesn’t work. And quicksilver.blacktree.com is down. Sooooo…. if you’re having trouble with Quicksilver in Leopard go to the blacktree homepage and download the latest version right from there, and replace your old version.
On a similar note, Spotlight and Finder are definately much faster, but after about 5 minutes I knew there was no way Spotlight could replace Quicksilver. There are too many “learned” shortcuts and custom key commands.