I've only been here for shows, having been to many a punk show here in my high school existence. The venue is a great open space without being overwhelmingly large, they've got a great stage that's reminiscent of high school gymnasiums turned up a notch, and they continue to have awesome local shows with decent sound.
And they do lots more than host bands, they seem to have all sorts of jam sessions and craft shows, among other things. Check out their website and you'll see a calendar jam-packed with events, something's going on every day of the week.
If you see a show happening at the Tranzac, definitely check it out. Also seems like a worthwhile place to host a party (if you can afford to rent the place out).