i think IQ is not as important as 20 ppg, but it is still pretty important. remember, F represents the IQ a of a low end college player, these guys aren't going to be "running into each other ;)" - just like 1 speed is a low end college player, not a 50 year old man who weight 400 pounds.
when you play top teams coached by top coaches, if you are a top coach with a top team except you haven't practiced IQ, im pretty confident you will get slaughtered. when you have a talented team and are playing coaches who aren't really paying attention in the regular season, who don't really know how to coach their teams, and you have been players who have grown faster - its a hell of a lot easier to come away with the win! there are so many things the other coach is doing wrong (a bad team setup can easily be 10 ppg) to make up for your lack of IQ. but play at a high level of competition - that space is just not there. or at least, i think its not. i have a pretty long history of watching the impact of IQ on my teams and it is damn hard to win a championship even when you have B+ iqs, not to mention Fs.
also - to the guy who said Cs should maybe be OK but Ds/Fs should be horrible - there are two possibilities with IQ - either the difference from an A to a B is the same as a B to a C or D to an F - or there are increasingly bigger jumps as you go up, to go with the vast increase in minutes it takes to go up each successive prestige grade. many believe the difference from an a to a b is significantly larger than a d to an f. i dont know for sure, but i would guess that is true.