LA Noire looks amazing. That much we can establish. And with Rockstar's guiding hand, we can assume that the gameplay would be pretty solid, too.
However, games like LA Noire will rely heavily on the strength and quality of their scripts in order to succeed and gain critical reception.
The last few trailers have been mildly worrying. It appears that Rockstar is going with a typical "catch a serial killer" sort of script. While murders are probably the most fun to investigate, it could open a big can of worms, particularly if the murders, the murderer, and the reason why the murders were committed are not tied together very well. And of course, the game claims that it's going to incorporate municipal corruption, moral ambiguity, and drugs as elements in the story, and we have yet to see how that will pan out.
Remember how one of Far Cry 2's trailers mentioned drugs? There were no drugs to be seen.
I, for one, hope the script doesn't suck. LA Noire is certainly one of the more unique games to come out this year.