Ok like what else is new. I finally come face to face with the injustice of this policy today.
I am flying the redeye from EWR-LGW and purchased a K fare on Thursday in order to be able to upgrade with miles.
The upgrade went through for the return segment (Nov 10th) but the departure (Nov 4th) didn't because of the 3 day rule.

Checked in and tried to talk my way into Business First. The agent said there were 9 revenue seats still unsold. Whats the chance 9 people are going to show up 1 hour before an international flight and snap up the seats. Why won't they release the seats to people already on the flight that are willing to use miles.

I know the idea here is for Continental to make money and not give up a possible revenue generating seat and give it to an upgrade. But come on, 9 seats an hour before the flight? I talked to the reward & elite lines and they said "we would rather the seats go empty than give them to an elite for an upgrade".
Now I fully understand what all the furor is about. You try to remain loyal and when you finally ask for a little something back, BOOM. My 2 cents. Let the rants begin. LOL