Remember the issue about KeyFinder and accented characters?
But of course you do.
Lion, I recently discovered (Pogue, p 238), has obviated all necessity for such, albeit by changing keyboard behavior somewhat.
Holding down any letter key delivers up most of the possible character diacritics one could need/want and selection of same is a simple click away.
Incredible! Unglaublich! Incroyable!
Lovely! Schön! Merveilleux!