Bader is a solid venue! I've been only a handful of times during film festivals, but each time has been a great experience.
It's a lovely building with very modern/clean design, and the three levels seating spreads out the flow of crowds filing in for screenings pretty well. Seating is comfortable (though it can be a squeeze getting in and out of full rows at times!) and the sloping of rows is enough that you won't have an obstructed view.
Audio and video are excellent quality, and the sound for introductions (with or even without microphones) is quite good. I have only ever been to screenings and been seated on the floor level, so I can only assume that all of the above is true for the upper levels as well.
Washrooms are all the way in the basement level, but there are plenty of stalls and i've never seen a lineup. No concession stand, being just a simple venue - I think it'd be great to at least have a bottled water vending machine somewhere though, watching movies is thirsty work! There's a nice lobby area for people to loiter, leaving enough space for people heading in/out of the venue.
If you have an option of seeing a festival screening at the Bader, I recommend it!