If you're drinking a good beer, or even a beer that just claims to be good, you can't really judge it fairly unless you pour it in a pint glass. I'm not really sure what the reason is for this, but many beers taste distinctly different in a bottle than in a glass, and the flavor in the bottle is generally worse. Some of the complexity of the beer's flavor seems to get lost, and whatever the strongest element is tends to get exaggerated even more. “Old Rasputin Imperial Stout,” for instance, has a far superior flavor in a pint glass than in the bottle, where it sometimes tastes too hoppy. “Obsidian” stout is the same way.
Another factor is beer's temperature. The English like to drink their beer at room temperature or even lukewarm. I don't agree with this practice, but it is the case that most beers have more flavor at warmer temperatures. Keeping the beer really cold, chilling the glass or even putting ice in it (?!) will all tend to flatten out the flavor, so you only want to do any of these things in order to mask the flavor of bad beer.
The best practice, in my opinion, is to buy your beer at room temperature (the stuff on the shelf in other words), throw it in the fridge while you cook dinner, and pull it out when you're done. Pour it into a pint glass, let it settle, and you're good to go. Cheers!