Saw X-3 the other day. I enjoyed it very much and do recomend it. The theme of discrimination continues, only with a twist. As with any sequal it stays the same but is different. When I saw the first two I was very surprised how good they were. I thought they'd be horrible. I will say 3 isn't as good, didn't have as much depth (not that summer blockbusters are known for depth).
Tuesday I was told that I missed a key component of the story. It comes after the credits roll. So, if you see X-3, don't leave until the very end.