I am a HUGE Watchmen Fan, I'm even excited about the new Watchmen Comics (yea, yea, I know) - My favourite cut of the Movie is the Directors Cut (not the Ultimate Cut I hear you ask) - no, because the Ultimate Cut does nothing to enhance the movie. It just puts that bloody Black Freighter cartoon smack bang into the middle of it all slowing down the Action.
I know purists might insist its better with it in, and thats fine - of you go and watch it that way if you are so inclined.
I prefer my Watchmen "undiluted" LoL!
I recently came across a Fan Edit of the Watchmen called "Watchmen - Midnight" - and I must admit, I'm damn impressed.
It does take some of the more OTT Action moments out, but that doesn't really detract from things - on the plus side its edited to recapture some of the spirit, story structure, and character depth of the original comic books by reorganizing/trimming scenes, adding new content from the “Under the Hood” documentary, even to the extend of replacing music to change the tone of various scenes.
Though its slower and less showy, its well worth the effort in tracking it down and giving it a look-see.
Like all Fan Edits, you should really own the Movie - the Watchmen is worth it too IMHO.