do you think his draft stock was positively affected, negatively affected, or unaffected by Texas using the spread offense for many of the snaps Vince Young took?

I think the response to this question is simple: Vince’s stock was wholly positively affected by being in a spread offense. The Horns’ offensive scheme highlighted Vince’s strengths (athleticism, vision, scrambling ability) and made him more appealing to those in the NFL looking for “playmakers.” There’s the outside possibility that Vince in a pro style scheme would’ve had him positioned at #1 overall, but that takes in the assumption that Vince would’ve been as successful running a pro style rather than the spread. That seems unlikely, since the pro style offense he currently runs seems to highlight his major weakness, accuracy.

A fairer question would be whether you believe Vince’s time running the spread in college has adversely affected his ability to adapt to a pro-style offense. Had Vince run a pro-style offense in college, he may have been more successful in the pros.

Are College quarterbacks better off in pro style offenses? Does that necessarily increase their draft stock?

As to this question, I don’t think there’s enough data points (yet) to support an answer. Looking at past draft results, Vince is the exception rather than the rule. It appears that the only other “spread” QBs to be given as much of a shot as Vince would be Alex Smith (admittedly, a colossal failure) and Mike Vick. This is definitely unsustainable in the near future, and Sam Bradford will be the most interesting example, as unlike VY and Smith, Bradford is the “prototypical” NFL QB, yet he plays in a spread offense.