I think the argument that you can't take a NT at #1 is disingenious and oversimplification.
First of all I think the #1 overall can be more a curse than a blessing. No matter how high a pick you get you are never guaranteed a pro-bowler...but at #1 you will be paying them pro bowl wages.
Now the theory is to get the bang for your buck at this spot you have to get a certified game breaker. Normally people think of game breakers as QBs, RBs, Wrs, and LT since they are so hard to acquire.
However I make the argument that a game breaker is ANYONE who decisively changes the flow of the game from their position. If you acquire such a player, regardless of where the pick is, you have achieved worth from your drafting perspective.
Glenn Dorsey plays a position that is often away from the ball. So your casual observer doesn't see him play in and play out. However he is a beast against the run and makes an awful high number of sacks as well for the position he plays and attention he gets.
He can play both NT and DE in a 3-4 and Dt in a 4-3. Think about it. This is a guy we can line up all over the place in the front four and who will be the first focus of the offensive line on every single running play. How do you gameplan your running attack then?
So is Glenn Dorsey worth the number 1? is it worth the number one pick to go from being a sieve against the running attack to automatically elevating your team being a wall in the middle?
I say yes. Stop the run and punish the other guy with the run. Do both and you will win and you will win consistantly.