Nice breakdown, but I have to disagree about the defensive assessments. While I expect to see improvements at D-line, the LBs and the Secondary are surely question marks and it is not realistic to expect those two squads to be BETTER than last year. They might be pretty good, because last year's squads were none too shabby, so being slightly less successful than the '07 unit doesn't mean you're lousy.
That said, it may not matter at all.
The Doman-Staley would very likely have gone undefeated without Luke and Brandon getting injured at the last, and they did so in spite of serious defensive weaknesses. This year's offense might be similarly overpowering to its opponents.
Even if the defense is weaker this year than last year, it might be that BYU is able to simply outrun all it opponents as long as the defense is simply serviceable. The Detmer years proved that you can't have just one half of the team, so the defense will need to be at least something you'd call good.
But with the D-line likely to show improvement over last year, that might be all it takes.
That's why I'd say this year will be special, because the offense is likely to be so good, even a mediocre defense could create a third consecutive conference title--not to mention a possible BCS appearance.