I'd like to post a couple positive comments about my CO experiences.

Upgrades:
While I don't travel internationally anymore or transcon very often,I've been upgraded the vast majority of my flights, better than 90%, including NW on my OnePass number.

Reward travel:
Again, no international, very few transcon, but no trouble getting flights, although they are almost always standard rewards.

OnePass Service:
Without going into too much detail, I recently had reason to contact OnePass (via email). My request had to do with old, missing mileage. The rep I dealt with was fast, pleasant and efficient. I wound up with more miles than I thought (enough for a very nice anniversary trip).

In-flight:
Generally at least pleasant and usually quite friendly. And when I happen upon a flight with a meal (not very often), it's usually not bad, pretty good, in fact.

All in all, I'm very pleased with how CO treats me.

Again, just my opinion (and remember, I'm trying to increase my post count).