The main difference between the AP and the coaches' poll is that Boise leapfrogs both Texas and Florida into #3, and by a pretty significant margin as well. Though the AP is not part of the BCS rankings, this is a bit problematic as a trendsetter for the Harris Poll when it's first released later in the season if Boise manages to defeat Virginia Tech the opening weekend of the season.
I'm comfortable with the chances of an undefeated Texas only having to surpass either Ohio State or the winner of the Alabama-Florida game(s) (remember that they meet in the regular season this year) to advance to the BCS Championship Game. I'm a bit less comfortable with having to pass an undefeated Boise State as well.
(And for those who think an undefeated Texas would have nothing to worry about from an undefeated Boise State at the end of the season, regardless of preseason rankings, you're crazy. I'll be elaborating more upon that in the coming days.)