Overall impression: Surprisingly good, and well worth the cost of the ticket.
I think I'd read the book, and its sequel, several times over before I ever saw the Gene Wilder movie. As with most movies, you can't be a strict purist about the text. Some things are too complicated or too fantastic; other things are adapted to what the director thinks best. Besides, apparently Roald Dahl actually wrote the movie script, so if it's not precisely like the book, it's still well within the author's intent. At any rate, I enjoyed it for conveying the spirit of the story. I can sing the beginning of the Oompa Loompa song, like probably everyone else who has been a child since 1971.
Well, as far as accuracy to the text goes, I was blown away by this version. Melissa had suggested that I should re-read the book before going to the movie. I didn't do this, since the movie trip wasn't planned ahead of time. However, as I watched and listened, I was constantly noting little details that I remembered from the book. It even turns out that in this version, the Oompa Loompa songs actually use Roald Dahl's lyrics.
By far the majority of the changes that I noticed from the book were modernizations. Ordinarily I'm not a big fan of modernization, even of dated material. Very often it feels less like updating and more like inserting anachronisms to me. I didn't really have that problem here. The example that comes to mind is that Mike Teavee was obsessively playing video games, rather than watching westerns. It wasn't obtrusive, it didn't change the dialogue or the story, but it made it something that a child of the 21st century can relate to better. 
Now, there was one significant change that makes me add this to my list of movies that I would have liked better without the last five to ten minutes, and my objection is really presented in the movie itself. Paraphrased:
Mike Teavee: I don't get it. What's the point?
Charlie: It's candy. It doesn't need a point.
This is a fantasy movie for kids, based on a classic. It doesn't need a point! In fact, it's already got one built in - if you are spoiled and over-indulged, sooner or later you end up very unhappy when things go badly for you. If you are well-behaved and polite and good-natured, sooner or later there is a reward for it.
Apparently this wasn't sufficient for someone involved with the production, so an extra moral got shoehorned in about the value of Family Above All and Family Always Means Well. It fits, it builds off what is already in the story, it's not twisting anything... But the only really major change I noticed was that they changed the ending to emphasize this. It isn't bad, it's just something that I found unnecessary. It's candy. It doesn't need a point.
Johnny Depp is no Gene Wilder. Although, to be fair, he's not trying to be. He really does make the role his own. Willy Wonka is supposed to be a character who's completely over the top, and Depp needed to play it entirely differently than the equally over-the-top Captain Jack Sparrow. I just think someone (and I have no idea if it's Depp, Burton, or someone else along the line) erred badly in modeling Depp's portrayal of Willy Wonka after the present-day Michael Jackson. Creepy child-man who may or may not be a pedophile was never something that had been part of my image of Willy Wonka, and I could have happily lived without that. However, I think anyone who had never heard of Michael Jackson or who just didn't make that connection would enjoy Depp's performance very much.
Deep Roy played the Oompa Loompas. All of them. Individually. He was amazing. Melissa tells me he is one of the body doubles from Lord of the Rings, and he looks familiar from the documentaries, but IMDB doesn't list that as one of his credits. I'll have to check the credits on the DVD when I get home. (ETA: Just a rumor, apparently. Different little person.) Regardless, his performance here is outstanding. Basically, he is the running gag. And standing, and sitting, and singing and dancing, and rowing... I think I would have enjoyed the movie for his performance(s) even if I hadn't liked the rest of it.
The special effects were remarkably unobtrusive. Thinking back on it, the movie's full of them, beginning to end, but I only really noticed a couple of times. They must have been good. I'll have to watch it again at some point to see what I pick up.
I liked the music, but I suspect it may not be to everyone's taste. My memory says that it was a combination of Indian and disco, but then, that may be influenced by the Oompa Loompa dance numbers. Regardless, it was stuff I would tend to like as background music when I'm cleaning house and want something upbeat.
And, possibly unique to my experience, the scene with Veruca and the squirrels reminded me of a story I've heard about physicsninja.
 Of course, I generally say that I have no memory for details. Apparently that isn't so. I'm just so full of the details from children's books, advertising jingles, and stories from my mother's childhood, that there's no room to cram any more details in, and no room to organize them neatly for retrieval.
 And they couldn't have had him watching reality TV, or he would have figured out what was going on and refused to touch anything unless Charlie did it too. Right?
 Which he did very well. And, good lord, how that supposedly straight man can swish and flame. I still don't think PotC lived up to the hype. I know I'm part of a very small minority in this. It was good, it was fun, I enjoyed it very much. Once. It doesn't have lasting value for me, aside from the soundtrack, which I'll freely admit is incredible.