At absolute best, he'll get about 35 TDs and 4500 yards, an excellent season. Why risk that when Eli Manning and Matt Ryan will both reach 30 TDs and 4000 yards at least (barring injuries of course)? Not to mention the latter two are going several rounds later.
I don't expect Peyton to get injured again, he just won't be 100% and is not worth where he's being drafted.
Romo's an interesting case. I was high on him last year, and he did not disappoint (until the Eagles game where he got hurt, just added on to my playoff woes). While he should be up there with Eli/Matty for a 4k+ yd, 30+ TD season, I'm worried about his offensive line. That, combined with the lack of depth at WR and Witten having a chance of missing the season, and I'd look for safer options there too.
As you can tell, I'm kind of picky about quarterbacks... I'm going to be sad if I can't get Eli, Ryan, or Rivers :(