It looks like system-cleaner will be in Ubuntu 8.10, also known as the intrepid ibex.
system-cleaner is a program I wrote for Ubuntu to remove cruft from systems, and to tweak configuration files and otherwise freshen up a system so that it is similar to a newly installed system. The installer will do things like put modern mount options in fstab. Someone upgrading from an old version won't get that. They might also have a bunch of obsolete packages installed. system-cleaner provides a way to fix those things easily.
Once Debian lenny is released, I do intend to upload system-clenaer to Debian as well.