I think the Texans are actually pretty difficult to review/preview. There are a few ways to think about the team. First off, the Texans have been performing remarkably consistently the last couple of seasons, making the playoffs despite some nasty injuries. The team is fairly balanced on both offense and defense, and even though they have some holes, it shouldn't be too hard to fix some problems and have another solid run.
That said, there are some serious problems for the Texans too. Most noticeably is the rise of the Colts. With Andrew Luck under center, it's clear that the Colts have a solid foundation upon which to build. While they probably aren't as complete a team as the Texans are currently, they might be able to catch up soon enough. A couple of years can change a lot in the NFL, and the Colts are looking up.
In addition, the Texans have some problems of their own. Age is becoming an issue. Matt Schaub is on the wrong side of thirty, and while he is likely peaking, his durability issues beg the question such that we must wonder how much longer he can play at this level. Again, he has some time, but one wonders. In addition, Andre Johnson is also getting up there in age. Unless the Texans can get a number two receiver to complement him, the team might struggle to keep the offense chugging along like they have the last couple of seasons. Moreover, the Texans should look at shoring up their offensive line, especially on the right side. As well as TJ Yates was able to fill in for Schaub, I think it's clear that the Texans are a better team with Schaub under center.
On defense, the Texans have a few areas to fix. Maybe the biggest need for the Texans is at Inside Linebacker. I imagine that will be filled in the draft. If the Texans don't retain S Glover Quin in Free Agency, which they should, they will also need to look for a new Safety.