A new review in the Philadelphia Bulletin gives another great description of Tom Felton’s acting in “Harry Potter and the Half-Blood Prince:
Rupert Grint is not a great actor, but he gives a solid performance now as a young adult. Daniel Radcliffe turns out to be a very good actor. And Emma Watson, as Hermione Granger, has grown into the strongest performer of the lot.
With one exception. Tom Felton, who plays the thankless part of the bully, Draco Malfoy, was cast BEFORE anyone knew how vital and difficult a role his would be by the time the sixth film rolled around. In many ways this is his movie — his choices provide most of the suspense. And he has to play them in virtual solitude.
It is hard to be sure, because he says so little in this film (yet conveys so much!), but he may turn out to be the best actor to come out of the child casting in the Harry Potter films. (And I include in this Robert Pattinson, who graduated from playing Cedric Diggory, who dies tragically in GOBLET, to giving a surprisingly effective performance in the difficult role of Edward Cullen in TWILIGHT.)