Depends on the genre and the particular game. But to be honest I've seen few games where I considered the boss battles just irritating - not counting the bosses who just are too hard (for example I considered the first boss battle in Devil May Cry 3 ridiculously difficult, at least in comparison to the challenges you had to deal with up to that point). But Dawn of War 2 would certainly be a negative example. It was a very bad attempt to make the gameplay less monotonous - at the cost of introducing both gameplay and content that just doesn't fit the rest of the game. The battles were long and boring and it just seemed absurd that a squad that just decimated legions of minor enemies would have such trouble fighting one guy whose looks suggest that he should only be slightly stronger than his buddies.

Generally I appreciate boss battles a whole damn lot, many games just won't feel complete without them and a "no boss battles" philosophy seems absolutely moronic to me. That some devs fail to create good ones doesn't mean that they are a bad idea in general. :P