I was lucky enough to get my hands on this beast of a camera just over a year ago! Here is my review of it so far!
The Bronica SQ-Ai is simply, a beautiful camera! When you hold it and feel its weight, you know that you are handling a well-engineered piece of equipment! They just don't make them like they used to!
My set up is the Bronica SQ-Ai body, with a 120 film back, 80mm 2.8 lens, and a waist level viewfinder.
The viewfinder is perhaps the most impressive, really big and bright. Its a joy to use. If you have used WLV's (waist level viewfinders) before, the Off-Axis thing takes a while to get used to. I usually use this camera on a tripod when I can, which is a bit of a pain as if you are shooting at eye level, you have to be 'above' eye level, in order to look through the viewfinder. You can buy a Prism viewfinder to solve this issue, but I don't have the money at the moment!
The camera is fully manual, without even a light meter, so an external meter is needed. I believe that one of the prism viewfinders has an in-built meter though. You can also add a speed grip which makes it more durable and 'SLR' like, which would be better for more documentary style shooting, as being set up how I have it, it definitely suited more for studio work!
All in all, it's a beautiful camera, and gives beautiful pictures! The lens is super sharp!
If you get a chance to try one, def do!