I don't have any problems with NW flights, myself. I do think that CO F/C is a bit better (sundaes), but nothing I'd really consider when buying a ticket.
The biggest factor is EQMs and FC upgrade. I have a trip to Philly tomorrow. One leg is on Continental. The other 3 are on NW. Care to guess which didn't get upgraded?
I get treated well on NW, no need to buy the tickets on nwa.com, their Biz Perk program is a nice bonus, and plenty of upgrades. I would hope for more international upgrades, but hopefully in the future. At least they're not gutting their FF program, and they have decent availability for miles.