colocated branches support

[Wichmann, Mats D]

Pardon for what's perhaps a basic question, but...

how far did the implementation of colocated branches get in bzr 2.5?
I did some experiments with the plugin based implementation in 2.4
(bzr colo) but then didn't swing back around to try with 2.5.
Is this stuff well documented?  What happens to the colo plugin?

The release notes are not exactly verbose on the topic:

"The 2.5 series provides a faster smart protocol implementation for
many operations, basic support for colocated branches"

Thanks,

-- mats