I recently did the upgrade to Snow Leopard on my MBP. To my dismay, Quicksilver no longer worked. It terminated immediately after launch.
I found the the Beta 56a7 on here.
I also had to remove Plugins.plist and the Plugins folder from ~/Library/Application Support/Quicksilver.
I am ecstatic to report that Quicksilver is up and running again, and my Mac is happy.
For basic usage, B56a7 will do just fine, but for heavy users, this version will give us many problem, from lagging, crashing, etc. I finally, get around this by this method: http://tinyurl.com/yhsn8h6 hope it helps