I saw 300 yesterday with the comments turned on and noticed numerous compositing errors. These are however not as ridiculous as those of The Matrix Revolutions, which significantly lowers its visual effects prowess, not to mention that the human-shaped robots weren't so impressive either, even though they still pack a punch. The movie remains less-than-average, though more bearable than the last time I checked.
As for 300, it would be unfair to judge the movie itself due to the reduced dramatic impact caused by the comments (and Zack Snyder, the director, decided to turn the entire thing into a one-man show instead of giving the other filmmakers, who were with him during the commentary, a chance).