I have to disagree. All players run the 40 in similar conditions in regards to clothing these days, so using that as a reason to disregard them seems like a logical fallacy to me. If "player A" runs in shorts for the same distance in similar conditions as any given "player B", then the times over that distance can be used to differentiate velocity (d/t) between players. I realize that the game is more about short space agility and sudden burst/reaction as well as an infinite amount of technical skills, but to say that 40 times are garbage seems a bit harsh to me.
For every player who was great while running an average 40 time (Rice's 4.59 and Smith's 4.60) there are thousands of players who graduate every year who don't even have that speed and athletic ability to make it in the NFL or any other professional football league.
Rice and Smith were able to overcome average overall speed by having great instincts, vision, burst, and agility in the open field. Having those abilities trumps overall speed IMO. In fact, Devin Hester only posted a 4.35 at his pro day in 2006 and a 4.42 at the combine, yet, he has the ability to take a punt the distance on any given play. Why? Because he has elite vision. Watch some of his returns. He usually makes one cut and goes. He is able to see the blocks develop and find a crease in the kick coverage...then...exploit it. He was never worthy of a 100 SPD rating as EA erroneously gave him in my humble opinion. However, his BCV and JKM ratings should be off the chart. I think too often casual fans confuse more intricate abilities with overall speed.
Heck, even in the Super Bowl in 2007, Hester was ran down by Matt Giordano of the Colts on the opening kickoff and he only ran a 4.48. Yet, Hester was able to get into the end zone before he could be caught (and that's even after Giordano had to run downfield, disengage a block, and weave through the trash before getting an open field shot to run him down).
http://www.youtube.com/watch?v=MVT91mNMS8A
Madden does not currently do a good job of differentiating between skills. Basically, if a guy is fast, they boost his SPD, AGI, ACC, JKM, and SPM, when in reality a guy may be fast in a straight line but can't cut for beans. The opposite holds true as well (see Jerry Rice; not great overall SPD, but amazing ACC and open field agility). This is something that needs to be better represented all while utilizing some of the measurable standards. I guess I ask this. If the 40 times and testing results were not important, why would the NFL coaches and scouts waste their precious time in the offseason on going to the pro days and combines aside from simply meeting with the players?