And Java 6 arrives with a bit of controversy.
Ted rants about the lack of a 32 bit version in Why, Apple, Why?
In a nutshell, if your Mac has a Core Duo CPU, you're running 32 bit. You must have a Core Duo 2. (see this Wikipedia entry). Oh, you must have Leopard (10.5.2) as well.
Here's a great post that shows you how to make 1.6 your default Java. The Apple installer doesn't do that... apparently they don't trust the version enough to be the default Java on your box. Not inspiring confidence with that decision...
Man, I really love Ruby.