So first, the good things. One, these movies are epic. They do a great job with the sense of adventure and action, putting you into an accurate representation of Middle-earth and its denizens. The dwarves are drunken idiots that are a lot of fun. Gandalf is Gandalf. The elves are serene and elegant jerks. All of the monsters are believable. Except for the mountain giants. That was unrealistic just for the sake of action.
Second, the general plot is actually very close to the book. Very few things were left out (though sometimes the order was mixed up). I suppose a lot of that can be attributed to the fact that they needed to add stuff to make three movies, so removing things would have been counter-productive.
Third, there's three movies. Sure, they made three movies out of one small children's novel, but it's still more Middle-earth movies! Don't complain about that.
So a lot of people talk about how its inaccurate, but they're mostly pointing out the things that they added to the movies that weren't in the book. The white orc, Legolas, that kind of stuff. Let me get this straight, I absolutely hate the love triangle in the second and third books. As a rule, I hate the trope of falling in love over the course of a book and novel, and I'm very critical of the execution. Movies like this have no place for it. Also Legolas shouldn't be in this movie at all.
The second movie is basically the worst movie of the three. It's focus draws upon the love triangle quite often, and its ending is really weird. It's very strange if you've read the book.
So, all in all it's okay. I would watch the trilogy again, and probably enjoy it, too. It's got a few holes, and there are things that irk me, like the fact that they literally don't even bother to introduce half the dwarves, but it's good. I'm sure they did that because people wouldn't remember names anyway.
Also, minor spoiler, Legolas' father tells his son at the end to go meet Strider (though he isn't mentioned by name), but that is stupid because one, Thranduil hates men, and two, Aragorn was ten at the time! So I guess there's also a discrepancy between movie canon and book canon. I mean duh, but what I mean is that the order of events and the time spans between them are somewhat different in the movies. I'm not really sure. I don't claim to be a Tolkien expert, I just know a little bit more than the average person.
Double P.S.: Bilbo's riddle game with Gollum is pretty much perfect.