I. Loved. X3.
It totally had a better plot and storyline then X-Men 1 and X2; I liked how Storm's role was done more like the cartoon-Storm's role, as well as the other new X-Men that got added to the cast (I'm looking mainly at Shadowcat, Spike, Arclight, Psylocke, and Juggarnaut)
The Phoenix bits were a creative twist in the movie; though it wasn't really accurate based on the comics (ex.: how Jean became the Phoenix, and the whole Saga of it), it was nicely touched up in less than 2 hours only. Her relationship with Cyclops/Scott was very poorly done in X3, though it was nice to see them in love again near the beginning when Jean made her appearance

. Oh, and her powers rocked at the end of the film....
Callisto vs. Storm! They had that sense of rivary in the movie, just like how it was in the cartoons and comics. I don't recall Callisto ever having "super-speed" in the comics or cartoons; it was more like stamina, but I guess the director wanted to twist that part too to have an even match between the 2.
As for Rogue, although alot of fans complained about her not having her super-strength and flight powers, I found it awesome how the director (as well as the director for X-Men Evolution) had Rogue stuck with just her own, natural powers, which was the ability to absorb memories/life-force/powers from other mutants/humans. They kept her "as she really was" with her own gifts, and alolowed her to shine on a few occassions just with them. I did miss her sassy, flirtaous nature from the comics though
haha, yea; as you can see, I SERIOUSLY loved the movie. I've been a Marvel geek for quite a while, and I'm glad that there are directors were willing to try to make films on my fav comics
I can't wait for Spiderman 3 and X4 to come out!