Slate covers the word "sucks" quite eloquently in an article "Suck It Up - A defense of the much-maligned word" [slate.com]:
"Sucks is the most concise, emphatic way we have to say something is no good. As a one-syllable intransitive verb, it offers superb economy. Granted, some things require more involved assessments (like, say, James Joyce: I find his early work unparalleled in its style and its evocation of emotion, while his later writing became willfully opaque in a manner that leaves me cold). But other things don't require this sort of elaboration (like, say, John Grisham: He sucks)."