No way does he let the movies down! Fair enough, Rupert Grint is probably the best actor of the three of them, but Daniel has so much more to do and always does it well.
I did think he was good in the fourth one, and I will reserve judgement until I see the film, but I'm not hopeful after what I've seen in the trailer. Though he does only have two lines they sound wooden. I do however, like him as a person and I think he has charisma on screen.