Rather unanimously accepted assumption by Lombardi, Casserly, Mayock, Dukes, Davis, etc.
In addition, I am noticing several rather reputable draft sites show Gabbert as the #1 QB in the draft (or rated higher than Cam Newton).
http://www.drafttek.com/positionalQB.asp
http://www.nationalfootballpost.com/scouting_department.html
http://www.draftcountdown.com/Rankings/QB.php