One must also consider that some roles....just seems to surprise the hell out of you with what the actor does in portraying them compared to the actors previous performances. Give benefit of the doubt until you have the evidence in hand of having watched the movie.
Instead of a chance of being pleasantly suprised I would have prefered the casting of higher caliber, more famous and more liked actors such as Matt Damon as Kirk, which in this example would have been possible as Damon was interested in the role.
the problems with casting a well-known face to play another well-known face are manifold. one, there's usually a lot more pressure of performance. two, JJ is a well-known director (at least, here in the US) and he might want his own stamp on the thing instead of it being called Matt Damon's vehicle. this way, it'll be JJ's baby, not Matt's (which would have happened, trust me). three, Matt isn't that great an actor, IMO. so you're sort of defeating your whole argument there anyway.
I much prefer it this way. both Quinto and Pine show promise. in fact, they're much more like Nimoy and Shatner were in the '60s... they show promise, have had a few interesting film and TV roles (Pine has had Smokin' Aces and Quinto his Heroes just like Shatner had The Brothers Karamazov and Nimoy had... well, maybe not so much). most importantly, they are both hungry actors (just like Shatner and Nimoy were back then). hungry (not in terms of food, but roles) actors are always a better bet in Sci fi than worn ones. Damon also does not fit the look. he's way too old, and way too familiar. we need a young Kirk and a young Spock we DO NOT KNOW YET. hopefully, we'll get to know them both, in a hurry, come May 8th.