Good thing because we all know that Klingons use disruptor cannons. That has been a given for... I don't know how long. Only reason for Kirk's promotion is because Orci wanted him to be Captain at the end, for no logical reason. It wouldn't have made any difference on the success of this movie (yet it would have given this movie a little more credibility). They could have made Kirk Captain in the middle or beginning of the next movie.