We've recently seen many breakage in the X server and the mesa/DRM subsystem, however these have been associated with significant performance improvements.
Things are rarely broken just for the hell of it. I don't the the changes themselves are so problematic, so much as the fact that they are out of sync.
And we know it's not the main issue, because FreeBSD which is careful to avoid any sort of breakage doesn't have a flock or ISV's purueing it. The main issue is simply users.