Mountain Sun Pub and Brewery, visited on 4/5/12 (http://www.mountainsunpub.com/)
I've been to their sister restaurant in Denver a few times and it's always been packed. Holly and I stopped at the original location in Boulder off the Pearl Street pedestrian mall prior to hitting up an Explosions in the Sky show at Boulder Theater. It wasn't tremendously crazy, but still quite busy. Here's what we tried:
Hop Vivant - 10%abv; 8 oz. pour; I believe this is their seasonal imperial IPA; it's almost red in color; crisp looking; light lacing; very small head; very grapefruity on the nose; a little sugary on the nose as well; this beer tastes like fruity pebbles; good and easy hop taste, but not overly so; really soft in the mouth; I don't notice any overly heavy malt flavor; the beer lingers; hints of anise with a mouth swish; slightly bitter too; the beer sticks to your throat long after a sip; this is a good beer.
Nitro Old School Stout - unsure of the ABV, maybe around 5-6%; there's a dark look to this beer, somehow like oil; there's a nice light-looking tan head as contrast; moderate lacing; quarter-inch head; heavy malt nose; the beer is smooth poured via nitro; tastes very roasted; good light stout flavor; decent sessionable stout.
FYIPA - huge head!; 7.2%abv; again, real big head...almost a full inch and dense; dark amber in color; sorta cloudy; good lightly citrus on the nose; good hop-forward beer; 'American' hoppy - dry, slightly bitter; heavy grapefruit flavor; packs a punch too; I really like the taste of this beer; it's been dry hopped and it's noticeable; I could drink 3-4 and be hammered; good flagship IPA; Holly thinks it tastes like perfume.
Cleveland Brown - love the name by the way, an apparent ode to Family Guy, or the worst football team in NFL history...both are comical; Holly ordered this beer in an 8 oz. pour; 4.9% abv; again, dark and malty; we have a first-day waiter...this may have been the stout ordered twice, or the hops have ruined my palate!
Full menu here of a lot of tasty items; real good bar-food eats with vegan options. I had a good buffalo chicken sammich; Holly had an ok quesadilla; Good food and good drink offerings...a mandatory stop if you're poking around Pearl Street with nothing to do...or before a show at the Boulder Theater.