I didn't see another thread on this topic, surprisingly.
Well, I was never a big follower of the X-men line of stories. I went into the first one thinking it was going to be a cheesy comic book movie about some people with superpowers, and was presently surprised by a fun movie.
Today, I went into X3 expecting a fun action flick, and I was presented with the cheesy movie I expected the first time around. I thought it was a bad movie: not "Wolf Creek" bad, I could still sit through it, but bad.
I blame a lot of it on the writing. The dialog was horrible, and as the woman I saw the film with pointed out, there were no Once and Future King references at all.
The way they dealt with several characters, without saying anything more due to spoiler's sake, left a LOT lacking.
In the end, I found myself not rooting for one side or the other, but rather for the end of the film. I give it a 5/10.