Scotiabank Theatre is probably the largest theatre downtown and usually features the latest releases. There's decent selection of Ultra AVX, Imax and regular movie screens. It IS, however, one of the more popular theatres so I'd suggest getting AVX tickets or going early if it's a new release.
In terms of the food, my favourite feature at this theatre is the freestyle Coke machine where you get to mix and match different soda flavours. Admittedly, I have made MANY disgusting concoctions in the past but Lime Cherry Vanilla Strawberry Coke sounded good in my head.
Chairs are pretty comfy but I noticed more recently that my seats have been squeaky so I had to play the "don't move at all during the theatre unless you want evil glares" game.
Finally, let's take a moment of silence for the loss of Chapters next door. What a great place to kill time before the movie.
Just a word of caution, if you're going to a movie on an evening, remember that you'll be venturing through the Entertainment District. Beware of the vomit-stained sidewalks.