We should trust Nolan because of his history of choosing people in this series. Nolan picked Bale while he was at his Machinist weight, based on the conversation they had and the determination in his eyes. When it was announced that Ledger would be The Joker there was a huge backlash, only to have it all quelled when the prologue was screened and it was apparent how amazing that performance was. Nolan has acquired a very good reputation as a filmmaker, and for good reason. Rotten Tomatoes seems to be a fairly reliable source for determining the quality of cinema and Nolan's lowest movie on there is his first, which is only at 76%. I'd say that's still quite good for being his debut. As for fans of the franchise having issues with his representation, that's going to happen with everything. There are always people that have it set in their head how a character should be, and when there is any deviation from that they are going to dislike the version in the film. That doesn't mean Nolan chose badly, it just means people aren't able to let go of their strict expectations.