important security tip is to uninstall all old versions of the Java VM
Yes well, if you want things to stop working ...
There are two main reasons for having Java installed.
(1) You are running some desktop applications that are written in Java.
(2) You wish to run some Java applets embedded in web pages.
The security risks are mostly with (2), and the suggested workarounds, such as disabling Java in the browser, are mostly aimed at this scenario.
If however you are in scenario (1) it is quite likely the case that each Java application you rely on needs a specific version of Java (each version has its own bugs, so each application might be targetted to a specific version). In this case uninstalling old versions will kill the applications that rely on them.