At least for the adult viewer, this was the best in the series, largely due to the decision to cut the movie in half. The first Potter film was iconic, but uninspiring. The second was more interesting, but lacked acting chops. Both had an immature feel that turned off a lot of older viewers, but was acceptable given the subject matter. The third was perhaps the best, but had a whimsical feel to it that didn't quite jive with the underlying premise. Movies 4-6 improved in terms of the story-telling, but had a "rushed" feel - particularly Order of the Phoenix.
The strength of Deathly Hallows Pt. 1 was in the pace. It moved briskly, but made a point to capture many of the "smaller" details of the books. This would not have been possible had the entire book been squeezed into one movie. The cast arguably put in their strongest performance to date. The story-telling is fantastic, full of drama and suspense. Therein lies the potential weakness of the movie; the intense story may turn off some younger viewers. Judging by the box office receipts thus far, that has not been an issue.
Highly recommended - I'd give it 4.5 stars if possible.