i'll answer pasteurization=improved? later...
better put a few thoughts down before i forget...
pasteurizing a beer affects it in two ways: biologically and chemically.
the heat will kill anything in the beer - yeast, bacteria, mold, etc. for a clean (non-sour and non-funky) beer, this is generally a good thing (as long as you're not trying to bottle-condition the beer). so for a beer like BCBS, which is force-carbonated before going in the bottle, pasteurization should be beneficial from a biological point of view. whatever bug ruined last year's batch won't appear again this year, thanks to the flash-heating. (aside: some sour/funky beers are pasteurized, like rodenbach or new belgium. their stated goal is to "freeze" the development of the beer - they release it when it's just the way they want it, and they don't want it changing in the bottle. i'm not a fan of this, i like my sours to evolve over time. let me decide when the beer is at its best, dammit).
chemically, pasteurizing does impact the make-up of a beer - and thus impacts the flavor. supposedly flash pasteurization, which a lot of breweries use, has minimal impact on the beer. i have not had the opportunity to taste pasteurized vs. unpasteurized beer, but i have had pasteurized vs. unpasteurized milk and there is a noticeable difference. the impact on beer might be different (maybe the fat in milk is more affected than the carbohydrates in beer) but it can't be positive IMO.
overall i'm not a fan of pasteurizing beer. beer is supposed to be alive. plenty of breweries send live beer out the door so it can be done.
however, from a business perspective pasteurization makes a lot of sense. GI lost a lot of money and consumer goodwill because of last year's infection.
