let's not get into the qs/lb fight here, but lb does the same (bookmarks, files, playlists, songs, address book entries etc.) -> but that's what i mean: Spotlight will be better for most of those items, quite probably.
On both LB's and QS's side, there's been discussion about how Spotlight might affect the utilities. And the consensus seems to be that both LB and QS will probably support Spotlight technology and become even better utilities than before.
LB's dev once said about this that LB's code is better for handling less files (i.e. handling the apps etc.) and Spotlight is better for _all_ files. And that, like I said, in order to use it as a launcher, LB (or QS, if you prefer the gummi interface) will still be the better choice.
For me it's quite clear that the Finder still stays my preferred tool for actually handling/sorting files, folders and their structure. I love column view for this (and list view for some stuff, too).