Thus is definitely a move in the right direction. There have always been issues with the GNU OpenJava project being well behind the current version of Java. As a result everybody installs Sun's JDK in Linux if they want to do more than run the (few) Java applications that ship with the main distros, but you can't remove OpenJava in case something breaks.
Now that LB4 encompasses Java 6 this issue will vanish and we'll reclaim a bit of disk space.
I really don't understand the comments about diccuculties with installing Java. In the RPM based distros it is a non-issue: download and install the RPM, change your class path definition to suit and its job done: no harder than slotting in Opera or adding a 3rd party jar file.