Java has a critical Java 6 update 29 patch. I have been reading some commentary about issues with 6 update 29. Since Oracle has released Java 7, we now two Java versions being updated. One thing I noticed is that Java 7 doesn't uninstall Java 6. I read that Java only uninstalls older versions of the version you have (i.e. 6 uninstalls older 6 updates and 7 will uninstall older 7 updates). Therefore, at whatever point you migrate to Java 7 and no longer require Java 6, you will have to manually uninstall Java 6 to remove it. The same would be true for Java 5 on your machines.
Also remember that some programs hard code to a specific version of Java so make sure you understand whether you have one of those hard-coded Java applications before uninstalling older Java versions or adding newer Java versions. CA and RIM are two examples of companies that have hard-coded their application for the Java version present upon installation. Here is Oracle's Java page: https://tiny.cc/mis40