I think it's important to differentiate between the different types of errors that you're handling. For errors that are caused by invalid user input, it's a good idea to create an error page that tells them what to correct in their input - probably including the current input you've got and pointing out what needs to be fixed.

For anything that is outside of the user's control (missing files on the server, invalid permissions, that kind of thing) I think that it's a waste of time creating clever error reporting pages. You're probably not going to give the user any information that will mean anything to him than the default web server error page and you run the risk of giving a passing cracker too much information.

The "vanilla" 500 Error page is fine for most purposes. Of course, there's nothing to stop you replacing it with another that better reflects the look and feel of your site.

"The first rule of Perl club is you do not talk about Perl club."
-- Chip Salzenberg