I worked at Buckfast Abbey for a year and those hives that still had Brother Adam's lines were a delight to work with. But, as with all 'pure strains', once they have crossed out with almost anything else, they can turn very nasty.
There are several places in Europe where Buckfast bees are still bred properly and they are still (according to the beeks there) as good as gold. Unfortunately, since Peter Donovan's retirement, the breeding program at the Abbey has fallen apart and they have many hives that are very hot.
I understand that Weavers in Texas had a franchise to breed Buckies, but stopped paying their royalties some years back. If their bees are now hot, it probably means they have not done the job properly.