I've been reading books like The Great Gatsby, Catcher in the Rye, and One Flew Over the Cuckoo's Nest in my English class, and compared to those Watchmen seems kind of silly. Really, the pervading pessimissim and misanthropy are kind of amusing. The idea of deconstucting the superhero, on it's base, is a worthwhile idea. But far too often the book starts going into these pointless philosophical ramblings, which do nothing to move the book forward.
These are good points, but I think we have to remember that
Watchmen was written in response to the Golden and Silver Ages of comics, in which every superhero was inherently noble and put-together, and every villain was inherently evil. Superman, for example, has always been the golden boy with little flaws and no inner demons.
Watchmen uses superheroes (as exaggerated examples of righteousness) to illustrate how dangerous it would really be if such exaggerated people were a little more broken, like you and me. This really is designed to serve a more political message about who we elect as our world leaders, and the kinds of beliefs, reservations, and biases they bring to office.
Alan Moore deliberately chooses to portray irony in his characters: the darkest characters are the most righteous, and the brightest characters the most corrupt. Even the chief antagonist carries out his horrible plan for larger, more complex reasons than just greed, vengeance, or the desire for destruction.
As for the characters waxing philosophical, I think there are underpinnings in the rhetoric that make sense after subsequent readings. Dr. Manhattan's chapter, for example, deals quite directly with the implications of the atomic age, where humanity begins to walk the path of playing God. (And he's a walking example of that idea.) Conversely, Rorschach's chapter passes judgment on the existence (or non-existence) of God altogether, which stabs at the heart of faith as well as the "superhero" as a dubious god-like construct.