Overall the movie was pretty true to the X-Men cannon. I noticed one or two small things they missed, and my brother filled me on the rest! Most of the ommissions could be blamed on trying to keep the movie going though I think. If your not a major geek you wouldn't notice most of them!
One thing that suprised me was that they did really tone down some things. I expected the scene where the fill Wolverines body with adamantian to be much more gruesome than it was. In fact, I expected to have to turn my face away during that scene (I get squemish!) and I didn't have a problem with it at all.
I really enjoyed the character development of the story. After all, that's what the movie is all about! The original trilogy left us with many questions (if you don't follow the comics that is) about what happened to make Wolverine who is. His past was a mystery made more profound by his lack of memory. All my questions were answered well, and the progression made a lot of sense!
I also enjoyed getting to know some new mutants. One that really surprised me was that one of the mutants (John Wraith) was played by Will i. Am of the Black Eyed Peas. I'm always a little leery when I see a musician or athlete jump into the world of acting, but I think he did a really good job. I was impressed at least!
The only thing that bugged me about the movie was the character of Victor, ie, Sabortooth. He seemed much more intelligent in this movie than he's portrayed in the original trilogy. My brother's explanation for that is that Sabortooth embraces his "animal" side more as time goes on. So by the time we meet him in the original trilogy he's barely a man anymore. I can see that as making sense, but I think they portrayed his character as too creepy instead of wild in this movie.
Did you know they are planning more movies in the Origins series? X-Men: Magneto is due to come out in 2011! I'm looking forward to it :)