I think Vic does a passable job as Kirk. He tends to speak through his nose though, and with practice could open it up and sound less like he's hitting the helium. And that's not a dig. I really think he's doing the best "non-sanctioned" Kirk I've seen.
The Spock guy is ok, but the hair bugs me. It's just not right. The ears are too big for his head too. These are minor things that can be fixed.
McCoy is miscast. The guy might be good with another character, but not this one. P2's John Kelley is much better, IMO.
Chris Doohan does a good job, but might be trying a bit too hard. Some places the accent didn't flow, like he was tripping over it. He'll get it right.
Another Scotty note: I thought that if it were 45 years ago, some of his lines would have gone to Spock or McCoy. Not a problem, just something I noticed.
Michael Forest was good.
The holodeck scene was weird. It didn't fit into the story at all. I didn't get the Paladin connection until I saw someone else comment on it. That's cool, but unnecessary.
Otherwise, the story was good. They hit the ground running with this one. Some things could be tightened up, but all in all, I've seen a lot