I always had a bias against O'Brien's as the *other* bar on 35th & Northern. Now that it's the only one, and some buddies of mine were playing a show, I finally caved and checked it out. Did not regret.
It's a pretty roomy bar that fits tons of people. I liked the enclosed smoking patio, since my friends didn't have to leave to light up.
The drink specials are groovy. $1 lands you some cheap beer (PBR, I believe) and for $3.50 you'd get a frosty mug of Leinenkugel's Berry Weiss. I can drink that for days! There are tons of cheap shots listed above the bar, and I'll get around to trying them all.
The only downsides were slow service (this place seemed understaffed) and no stage for bands. They just clear some stuff out of the way, and people there to listen to music find themselves bumping into people sitting down watching the game. Feels awkward and disorganized.
But if you get drunk enough, will that really matter?