Now that all the pieces are together, TV Guide has done a nice job putting a side-by-side comparison of the actors in the JJ Abrams Star Trek with the original actors. My first thought for Chris Pine was "no", but next to a young Shatner, he doesn't look half bad. Same thing with Karl Urban as Bones. I've been a big fan of Zachary Quinto as Spock since it was first announced. The other guys are passable, but as everyone knows, Trek was about the trio of Kirk, Spock, and McCoy.
Though, even if the casting was crap, I'd still be there opening weekend because that's the kind of nerd I am. :)