I only check for trips longer than 4 days, or when I do not have a confirmed upgrade and think there's a chance of waiting for one at the terminal.

It's actually the main benefit of being elite on CO (or any airline) - board while there's still room in the bins. I work off of the assumption that if you're not one of the first 10 or 20 people on the plane, you won't find room to wedge a waistpack in, much less a standard carry-on.

The new "crackdown" on carry-on luggage is a joke, and reveals the actual problem. They have NEVER enforced these rules across the board - making a system where cheating is the only way to have a chance. That's why people drag their portable closets on board - because they can. Just ask yourself how many oversize bags you've seen on any recent flight.

If there were benefits to following the rules, and liabilities for not, the system would fix itself. These are just a few ideas off of the top of my head:

$25 travel voucher or 500 ff miles if you do not bring a carry-on (bigger than a purse or lunchbox) on board.
All bags fitted through a "sizer" at the gate, no exceptions. $25 fine and / or forfetiture of seat (wait for the next flight) if you refuse to cooperate.
$25 travel voucher or 500 FF miles if checked bags are not available within 30 minutes after gate arrival.
50% refund of ticket price or mileage reward if bags are not available within 3 hours of gate arrival.

Believe me - with financial incentives for both sides, the problem goes away.

Sorry if I'm too harsh today - flying EWR to LAS in 4 hours, and not looking forward to the usually LOUD people in sweatsuits who's enormus carry-ons usually make the flight late.

Dave