How accurate have the draft "experts" been in the past?

It's crazy..I am not big on Manziel because his play outside the pocket, and his bust factor is a major worry...but you can't deny he has the "it" factor. The kid does play with heart and was impressive in the combine/pro day. Part of me wouldn't be mad if they swing and miss at that, because I guess he could be great...but with so many needs, I just don't know if we can take that gamble..They need to trade back if given the right deal.