Marquee Theatre is a good place to see a show. Not great, but good; and things have certainly improved since the remodel a year or two ago. It's a mid-size venue that attracts some good talent like Jimmy Eat World, Phoenix, The Used, Sigur Ros, Passion Pit, The Civil Wars and many other established acts who are too big for a small stage, but not quite ready to sell out arenas.
Marquee has always been a bit grungy, but that's part of the appeal I guess. There's a bar in the back and off to the sides inside the venue itself, but the line at the back bar is always obnoxiously long, i.e. don't wait til you're done with your drink to make a move for a refill.
I'll also mention that this place is close to Mill Ave and I've spent many a lovely evening getting grub and drinks before a concert then walking across the bridge to Marquee. Give it a try for those concerts with later start times (which is just about every concert ever).