I don't mind the changes in the plot, they were unavoidable but there are some jarring stuff (Kovacs big flashback with the dogs, the end to that has been modified for something shitty). In fact he should have gone way beyond, as it stands there is a lot of junk that could have been cut. It's a bit pointless to have the kiosk guy and the comics reader at the end when they were virtually absent during all the film : it's just a superficial faithfulness that highlights how Snyder is often just mimicking and playing make-believe. A lot of the "period" thing is also hollow, like the fake big nose of Nixon and Kissinger. Maybe the right idea was like Gilliam (I believe ? One of the directors previously attached anyhow) wanted, to make it happen in the "present" like the comics in its own time.
Regarding Rorschach, I also think it was handled correctly : The book is pretty ambivalent to begin with. He's pushed to the forefront a couple times more. Snyder upped the ante on the violence however (In a way, he's Rorschacing the film) and coupled with his abuse of slo-mo and bombast, it often made me cringe. Under all the production value there's moments where all of his bad taste comes to the surface and it is embarassing, the two worst offenders being the hilarious sex scene and the failed murder attempt on Veidt. Last major issue for me is the really bad pacing. They said Watchmen could not be brought to the screen and well... the movie proves the point. It's impossible to cram the backstory in there, and even with a lite version, it's still disjointed and long. So in the end you have a not so competent by the numbers blockbuster which is par for the course as far as Alan Moore adaptations goes (hopefully no one has yet seized Halo Jones so far...).
300 was not that faithful (but it's not Miller best work, I still like it).
The only Snyder film I like is Dawn of the Dead (and still... the director's cut starts bloating the movie), the only film adaptation where he went balls to the wall in the opposite direction of the source.
