I put them on for coding on intranet, but off when uploading to a 'real' webserver. It's indeed quite annoying having your logs filled with things like 'undefined variable' (e.g. from templates). I sync my real webserver with the intranet webserver tree (ssh dsa key), rewriting some files to get rid of debugging parameters automatically.

You could do fake initialisations to fool perl, too.

Either way, don't let it stop you from using things like 'strict' and 'tainted data' when coding.