BU is not a bad dental school. Matter a fact there is no such this as a bad dental school. Unless you attend a dental school you do not know the full extent of any of the problems they face.
Regarding BU, they previously had little problem with faculty. Currently i do not hear any complaints from BU dental students.
They also have very little hard time getting patients into their clinic. But in order to fix it they have been marketing very aggressively at cheaper costs than the treatment provided by the 2 other dental schools in the same state.
Personally, I would choose BU over any other new schools. I wouldn't choose bu over state school or other much OLDER private schools.
Older schools are much more research oriented, new schools are sort of like technical schools with no research, etc... Plus professors in older schools have much more experience running the clinic, research and their own private practice, and they will spread on that knowledge to you.
Hope this helps.