I just returned from the movie. I'll see it again before I make final decisions but here is my first impression:
I was disappointed in Silas, he wasn't portrayed in any way similar to the book. They didn't even give him contacts to look Albino - he was barely white, with white hair and the make-up was thin enough that he didn't always appear white at all, just white-haired.
Most major plot points were similar to the book, and most early deviations were understandable in the context of a visual medium with limited time. However, some of the other major deviations bothered me a bit. I won't get into details (for those that plan to see it) but I would estimate that you should expect 30-40% difference btwn the book and movie. (and that is a very low number compared to most adaptations, just look at Jurassic Park)
The acting was well done, and Ian McKellan was brilliant (as to be expected). The plot and story moved fairly well with only a few undue sequences to "spice the action" for the big screen. The ending was a tad disappointing campared to the book, but not untrue to story. I didn't notice any major tech problems and the cinematography was decent. The "eidetic memory" sequences were annoying, however and I thought Sophies role was watered down to allow Hanks' Langdon to shine more than the book version did.
All said I think anyone who has not read the book will probably like the movie, and those who have read the book will be split. If you are the kind that can appreciate differnces, you'll be fine. For those who get disappointed when little things are wrong, you will probably not like it. Based on its own merits, without comparison to the book, I would give the movie a 7. Decent script, few plot holes and decent acting. Hanks was a bit of a let down for me, but McKellan more than made up for it.
-K-