As the HP novels got heavier, the films suffered either by trying to cram too much in, or by cutting until the plot was incomprehensible. Cut the novel in half and suddenly there's room to breathe again: filmed refreshingly in 2D, HP7i has atmosphere and pace, with enough time on the clock to create authentic settings, linger on significant scenes or build tension. At the same time, the plot, slightly simplified, remains coherent although you will struggle a little unless you have read the preceding books. There's a lot of borrowing from Lord of the Rings as the Fellowship of the Potter travel magically around the world to seek out and destroy a Horcrux: this borrowing is the fault of the book rather than the film.
As with the book, there's far less humour than the previous films (though by no means none) and plenty of death, darkness and despair. The characters have grown up, but the actors unfortunately more so: Daniel and Emma just about pass as older teens, but if CGI can make Jeff Bridges or even Brad Pitt look young in Tron Legacy and Benjamin Button respectively then surely they could have done the same for Rupert Grint. However if the ageing is dodgy the acting and direction is awesome - all three turn in their best performances so far and you really get a sense of isolation, and how different their magical upbringing has made them.
Conclusion: full marks, and I look forward to HP7ii.