Of course highly touted QB prospects sometimes fail. Every kind of player sometimes fails -- even "proven" veterans. (It wasn't so long ago that Carson Palmer was an elite NFL QB, right?) So there's no such thing as a sure thing...but IMO that's no reason to ignore the best QB prospect in years.
Andrew Luck is the total opposite of lunkheads like Ryan Leaf and JaMarcus Russell. He's the classic "student of the game," the highly intelligent son of an NFL QB. He's in his third full season leading a pro-style offense in a major conference, where he puts up amazing stats and piles up wins. He has excellent poise, reads defenses and goes through his progressions well. He has sound mechanics, good touch, and throws an accurate, catchable ball. He has great pocket awareness, decent mobility and retains his accuracy on the run. He is a hard worker and a respected leader, on and off the field. Oh, and he's 6'4" 235.
IOW, if you don't get excited about that guy, who the heck do you get excited about?