The closest to an exception I can come up with is when you rely on image-based installs instead of package-by-package upgrades. And even then I can't manage to convince myself.
No exceptions at all for individual developers' machines.
au BufNewFile,BufRead *.js set makeprg=gjslint\ %
au BufNewFile,BufRead *.js set errorformat=%-P-----\ FILE\ \ :\ \ %f\ -----,Line\ %l\\,\ E:%n:\ %m,%-Q,%-GFound\ %s,%-GSome\ %s,%-Gfixjsstyle%s,%-Gscript\ can\ %s,%-G
Ha ha, only serious
Using both and suppressing the stupid warnings doesn't seem like a bad idea, if you can take the time to get it right.
That said, I suspect that this lint tool will catch some issues where technically correct code can make http://code.google.com/closure/compiler/ unhappy. If you're using the Closure library, that's kind of the whole point.
YMMV, but I get the above impression from the docs (How To) -- http://code.google.com/closure/utilities/docs/linter_howto.h...
Closure Linter is under Apache v2, which is GPLv3 compatible.