Yeah, I tried that out before I posted and found the same thing. The previous generation of Mac keyboards only went up to F15, and Quicksilver sadly hasn't been updated in a long time. It just doesn't have names applied to those particular key codes.
It's basically feature-complete, so as long as it remains compatible with the latest versions of OS X, I'm okay. If does not support Snow Leopard, I am not upgrading to Snow Leopard. A Mac without Quicksilver is no Mac at all.