Basically most of the time the NFL scouts get it right in the first round.
The rest of the draft statistically is quite the crapshoot for sake of at least feature performance by a drafted player who even makes a team for his rookie season. For most positions, the odds go down for sake of the chances of even making a team even further when you get to the fifth round.
Here as "Armchair GM" again in order below are my "overs and unders" for the 2011 NFL Draft, as in overrated players to be drafted and underrated players overlooked to be drafted and signed at a bargain or to be playing out of free agency:
Overrated/Poison Pills In 1st Round Cam Newton QB Mark Ingram RB Any QB But Gabbert Overrated In Late 1st/Early 2nd Round All Other RBs Jabaal Sheard DE Jerrel Jernigan WR Randall Cobb WR Underrated -- Projected In 2nd Round But Should Be Drafted In First Or Earlier In 2nd Martez Wilson ILB Justin Houston OLB Brandon Harris CB, Torrey Smith WR, and Leonard Hankerson WR Marvin Austin DT Brooks Reed OLB Drake Nevis DT Underrated Dark Horses In 3rd Round And Lower In No Particular Order Marcus Gilchrist CB Lawrence Guy 4-3 DT/3-4 DE DeMarco Murray RB Jordan Todman RB Dontay Moch OLB Edmond Gates WR Buster Skrine CB-5 DeMarcus Van Dyke CB-5 Jermale Hines FS Tori Gurley WR-4
In 2010 for your reference as a "Rookie Armchair GM", below are my few "overs"/underrated players who were all at least feature players with their stats and performances as rookies.
Of course overall I missed many others and/or was too optimistic including just plain choosing too many lower-round players for some positions.
Jimmy Graham, 3rd Round (2nd TE on my list)
David Gettis, 6th (4th receiver on my list)
Blair White, Undrafted, (9th)
Sam Shields, Undrafted, (6th)
Morgan Burnett, 3rd (4th FS on my list, but made starter at Green Bay as SS for Game 1 as he remained before being injured in Game 4)