from everything I've seen thusfar, does a better job of getting rid of the programs you no longer want.
Not unless you have analyzed the installation.
If you just use is as an alternative front-end to the add/remove applet (i.e. using the "Installed Programs"-tab) ZU just launches the programs own uninstall routine and thus does not do a better job than had you clicked 'uninstall' anywhere else.
(Okay, actually not entirely true as ZU tries to figure out where the program was installed and checks to see if that folder have been removed after the uninstall-routine should be finished, and if not, asks the user if (s)he wants to remove it, but that's it).I downloaded and installed a program called "Streamripper". It shows up in the program listing, but not in the list of available programs to uninstall. Is a feature to find the program and uninstall it plausible?
In what program listing?
Anyway, if it is not in the "Installed Programs" list, and you haven't analyzed it there's not much you can do other that find the program, delete its files and then try locating and removing its items in the registry. Manually. (Don't mess with the registry unless you know what your doing though!)
(Oh, and btw, when you locate the program files (e.g. the installation dir) check the folder out and see if there are any uninstall-routine present - it may just have forgotten to add itself to the correct part of the registry)
A feature that does this for you is (to some extend) plausible, but it will never do as good a job as if you had analyzed the installation...