I live in BOS and have been able to stay loyal to NWA w/relative ease. Then again, 99% of my travel is leisure, so I can be picky about my schedule/times/routes/etc.

Once you're at Logan (traffic getting to Logan can be an issue, as was mentioned earlier), terminal E, where NWA flies from, is easy to navigate through. It's small, lines aren't too long (usually), and there's even a 'secret' security checkpoint (near gates 1A-E, I believe) that is mostly deserted (i.e, no waiting). I'm not sure about MSP, but I know there are regular flight to DTW every 2 hours or so, so connecting isn't too bad.

Also, I found cheaper fares on NWA flying from PVD or MHT, both of which are within an hour's drive from BOS. The DL terminal (A), which is brand new, is also a pleasure to use.
All in all, I've been pretty happy w/NWA out of BOS!