I know the following will scream "metal elitism," but keep in mind that I detest Killswitch Engage because their music is total ass, not because it contains non-metal and mainstream qualities.
Even in my high school years, when I was first starting to get into the metal genre, I never understood the appeal behind Killswitch Engage. To me, they come off as another one of these shitty, MTV-friendly phony metal bands made to appeal to those that hate the metal genre (much like the Chicago-based mallcore disaster known as Disturbed).
Killswitch Engage's formula for their sonic diarrhea consists of trying-too-hard "hardcore" shouts mixed with emo whining about relationships that went sour, extremely half-baked leadwork, braindead breakdowns, and non-threatening, groove-laden guitarwork that makes Machine Head's lamest riffs sound like Dark Angel's "Darkness Descends." No joke, despite all the claims by this puke-inducing band that they're "heavy" and whatnot, they're merely an emo band with a "metal" glaze to them.
Now if you excuse me, I'm going to detox my ears with some Cannibal Corpse and Mercyful Fate.