Yes, lots of people over hype Bush, but you don't understand how amazing he would be for the Texans and in the offense Kubiak is bringing. Explosivness and vision are the two biggest things for a running back in a zone blocking scheme. Look at the players who are truly successful in this system and you will see they have these two things in droves.
Terrell Davis?... He ran a 40 in the 4.5 range but he hit full steam out of his cuts. That speed out of the break plus his vision for the cutback made him the first true standout in the scheme, NFL MVP, Superbowl MVP, and one of the few members of the 2000 yd club.
Clinton Portis?... His 40 is sub 4.4, and he has the blazing acceleration to match. 1500 yds in each of his first 2 years in Denver's scheme, and he didn't play a full 16 in either of those years. He was never an amazing tackle breaker either (he is now that he has added weight), but his first step was quick enough that people would be bringing him down with arm tackles.
Warrick Dunn?... Has had the best years of his career under Alex Gibbs in Atlanta. Dunn has quickness, and was never really good at breaking tackles. He makes lots of people miss, however, and he just had a career year. Once again, a guy with great vision, amazing quickness, acceleration, and a fantastic top speed.
Now lets look at Bush. He displays all the qualities that you need to excel in this system. He has explosive cut (and does it pretty much better than anyone), the vision, the ability to make plays once he is at the second level, the breakaway speed to make the running game truly dangerous, and excellent hands making him a dual threat.
He may not be the next coming of Gale Sayers like some say (of course he may just be that second coming too...), but in the Texans' new offense he will be the next Clinton Portis. I can garuntee that.