If I was you I'd wait another week. It is going to be added very shortly. Nick is just waiting for ace (obb maker) to fix some small bugs etc. My opinion is don't mess with anything as you can cause problems. Wait a week or so and it should be the new default BB.
Here is a thread regarding the OBB implementation.
I have checked it out, and installed it. Its really great, but still in beta. I no that rc4 doesn't have the bug the 1.4.4 had that ended up getting my bb comp'ed. I think it would be greate if we could keep XMB, and also add phpBB and maybe a few others. Why not?
Ya know what I'd rather see is a way to be more flexible with this stuff.
Instead of having scripts suddenly appear that you may not want to have and some that have been around for ages that should maybe be taken out . I'd rather see a method added to easily install or de-install to Cpanel. Maybe a WHM option to enable PhpBB, OpenBB, etc. A modules system adopted.
Being there are so many scripts with so many methods of installation, I know this is probably not an easy possibility.
I think it might be best to quit adding scripts until a better method is adopted. Maybe a good Forum and WebMail should be found but beyond that lets just keep it simple.