Made it to Sigma with X today. This game is much easier to play than X3 and also seems much shorter. Maybe that's because Zero has his own storyline. What I find strange is that Zero does not show up anywhere at all in X's story and I'm under the assumption that the roles will be reversed when I begin playing with Zero. There was also this female reploid from the opening video that hasn't appeared in X's story at all either, so I guess she's with Zero.
Anyway, like I was about to say before I went on about that stuff, Sigma, as usual, is cheap. This time, he uses an attack that I cannot dodge. It's as if the game is telling me to go back to previous stages and get more of the enhancement upgrades again. The first time it did this was when I made it to the first stage that I was supposed to visit after defeating the 8 bosses. The game made it impossible for me to make it to the boss without the leg enhancement, which made it possible for me to air dash. X3 did the same exact thing, but at a possibly much earlier time in the game, depending on how you go about doing things.