Easy to Upgrade
I have just returned from a long trip (over 20,000 actual miles). 5 segments were on CO and 3 on NW. I was upgraded at the airport for the majority of the flights, even 2 international segments.
I do like this new system of upgrades. No more silly coupons, just flash my elite card. Best of all, I did not call in ahead of time and was still upgraded at the airport. I was even upgraded on free flights that I used my miles to obtain!