It makes me laugh to think of someone reading the last book FIRST!! You need to have lived with Harry for the whole series to get what he's going through in Deathly Hallows. At the very least you should have read Half-Blood Prince because that and DH work as a 2 part story too.
I don't think DH is the best of the series, even though I DID think that when I first read it. Yes it features some of her best writing, but that's all in the last third of the book. A lot of the stuff towarRAB the beginning is a little tedious, and I feel they will cut the whole Ministry section out of the film even if they are making it in two parts.
Some scenes will work better onscreen than in the book, e.g. when Ron and Hermione have the big fallout because Ron thinks it's Harry she likes, not him (no doubt certain fans will be looking forward to the 'vision' Slytherin's locket shows of Harry and Hermione going at it). IMO that was crap characterisation from JKR because by this stage there's no way Ron would be that stupid.
What I'm looking forward to is seeing how dark they go with the part in the Malfoy's manor. Hermione is tortured, if I remember, and other bad stuff happens but it's more left to the imagination than anything. In the film (the second one this would be in) they could make it more extreme for effect. The Malfoys themselves should get a better payoff than in the book.