For one, the jpackage RPMs are not updated with any kind of frequency, and unless you are looking to involve yourself and actually learn how to create RPM specs, you are going to just be out of luck on a number of levels.

Second, the directory structures and proliferation of symbolic links to things like jars (which all have fun filenames like [junit.jar] with those wacky brackets). Test 1, install Tomcat 5 through jpackage, use it for a few months, then try to upgrade to a version not in the Jpackage RPM repository. Possible, but nasty. FHS compliant, but annoying as anything.

Third, installing Java via the RPM from Sun is easy enough, sure it isn't being managed by yum, but

Fourth, shared jars are kind of a PITA when it comes to classloader issues. Sharing commons-beanutils with a common install just because you can doesn't make sense.

Go ahead, try it, you'll see - jpackage will make you wish you had just downloaded tgz and followed the simple instructions.