Since the decision to demote ULE [story]
in favor of the 4BSD scheduler as the default for FreeBSD’s
5.3-Release, many improvements to both schedulers have been committed.
At the time it was marked broken,
ULE was especially needy in light of the status of its maintainership,
performance issues, and its unreliable nature in conjunction with threading and kernel preemption. Having resolved these problems, Jeff Roberson announces to -current that the ULE code is now in working order: More information can be found on kerneltrap.org.