Great for visiting Suffolk Law School
I stayed at Nine Zero for a workshop in June at Suffolk Law School. You cannot beat the location if you want to be near Suffolk Law; it is a short two blocks walk down Tremont Street.
The hotel was very nice for the conference rate; I don't know if I would pay some of the higher room rates described in other reviews given the other hotel options in the area. It seemed like a low-key W Hotel, but probably not the "happening" and "hipster" vibe it. The lobby and reception area is very small. And although they advertise a "wine hour" I did not see many people gathered for it. 
Overall, I think it is a great choice if you need to be around Suffolk but you will want to step out on the town for any type of socializing.