I've tried to run preview converter, but for some reason it does not work on my macpro with 10.4.11 (it's coming with something like the "...-001.TIF' is not a valid raw file - skipping" and i'm talking about p45+ raw files with, well, *TIF extension ).
In CO 4.1 I use "Make Web Contact Sheet" command. That works super fast, generating a 1000px jpeg gallery in seconds (ie. for 3-400 pics). This is imho way better than Preview Converter might do, because this way you can apply some quick settings to the images. (cropping, color temp., curves, etc).
HTH