Northwest's frequent flier program is better than Delta's, and MSP was just named the second best airport in the nation (the facility, amenities, restaurants/shopping, etc.).
HOWEVER, Northwest just cut food service, although BOS-MSP is over 2 hours, as is MSP-ANC, so those flights most likely aren't affected.
I don't know, maybe I'm biased, but who would want to change planes at SLC?
As far as service, I've had several incidences of really hideous service on Northwest, but to be fair I've also experienced decent service on them as well. Seems the DTW hub and crews are much nastier than MSP-based personnel.
An unexamined life isn't worth living.