The Phoenix is a thousand person concert theatre on Sherborne.
The good part is that it's a really intimate spot for a concert, and a great alternative to the Guvernement (which is the same size). I saw Tegan and Sara here and it was epic. They also do a lot of different kinds of concerts for a mix of people, not just trend following stuff like some other venues.
The bad part is that it's on Sherborne, and almost every time I get off the subway and walk south to the venue, I get propositioned for sex. It's kinda a prostitute neighborhood, so try to go in groups or drive. It's not dangerous, just creepy.
On the weekends, it's a club, but the bouncers aren't my cup of tea and it's a little hit or miss when it comes to how rammed it'll be.
In it's hay day, it was the king of clubs, but there hasn't been much reno of any kind that I can see in at least 10 years.