Ubuntu 9.10 Computer Janitor

I have been running Karmic Koala since it was beta 3. I was really interested in the Computer Janitor application located in the System|Administration menu. Since I have not yet developed a full knowledge of the Linux file system and how everything works, tools like this can be very helpful. I have questions such as, just what files can I get rid of and when is it safe to do so? But when I run the tool this is what I get.

I have been running Karmic since October and I did re-install once in December after I ruined my video trying to improve the drivers. So now I ask the question will Computer Janitor ever show items I can delete? I posted the same question in a Craigslist Linux forum and really didn't get the answers I wanted. I was however told of another program Bleach, that is in the Karmic Koala repositories and is more robust. I have installed Bleach and I used it once. There are several options that have deletable items and the program sports a preview option. I will have to try out more options and report the results later.

Does anyone else have any experience with  Computer Janitor, Bleach or other programs that do the same things? I would like to hear about them in the comments.