I used Northwest Airlines back in 1999 to visit family and friends in North America. In total I made 4 flights from London Gatwick (airport code LGW) to Minneapolis St Paul (MSP) and then a connecting flight on to Denver (DEN). Later I flew from Denver to Detroit and after some weeks back to London Gatwick on a direct flight.

The plane was a DC 10 and I was seated near the rear. Apparently this gives you less fresh air, but I didn't seem to notice that. I sat in the middle section of seats, being on the far left of this 4-seat section. This may have given me extra arm room, I certainly felt better off than the bloke to my right.
Seats were made from blue upholstery. The tray either came from the seat in front or unfolded from the side arm. I found it a surprise and quite intriguing. As with most airlines, cigarette/ash tray deposit parts were also in the arm of the seat, yet smoking was prohibited at all times, as with most airlines. I think that's an excellent idea!
Easy to read and understand Emergency info cards, a "SkyMall" catalogue and another NorthWest Airlines magazine were in the located in the pouch in front. These provided some useful entertainment during taxing and landing when you basically aren't allowed to do much else.
A cotton/synthetic blanket was also provided and was found on the seat as your arrived. I would thoroughly recommend that you remove this before sitting even though you may have a bit of hand luggage. I sat on it initially intending to remove it from underneath me, yet with my seat belt on tight during taxing, this was impossible. I actually forgot about it somehow and realised after an hour or so. It was quite a relief to know the actual seat wasn't that uncomfortable.
To reassure you, life jackets were under the seats and are easy to remove (I gave them a little test, to see how easy the pull strap was to grab). Baggage space was available under the seat in front but this was kept away from the lift jacket and legs of the person in front. Extra storage space was available in the overhead compartments but I never use them since they're too impracticable.

The in-flight safety demonstrations were somewhat surprising. I was expecting to see stewards show us how to put on and adjust our seat belts, but to my surprise, they actually showed a video on the movie screen. This was obviously produced in the USA as the friendly personally welcoming style they used did make me laugh. It was easy to follow though a bit patronising.

The flight fortunately arrived on time and I made my way to the connecting flight in good time. At the baggage claim, I did see my bags come around on the baggage carrousel, so I took them with me to the departure gate. At the boarding gate they loaded them into the aircraft hold for me, but I was a bit puzzled since I was told the bags would be automatically transferred. Not sure if they were going to or not, but in any case I ended up doing it myself.

I eventually boarded the flight after allowing the usual rush of people to make their way on board first. Then I sat down and waited to be taxied to the runway. I then waited a bit more, then a bit more and then listened to their captain. Apparently, the air conditioning circuit breaker was faulty and they had to replace it. I didn't mind this much as I wasn't in a rush and an engineer came along to replace it in a reasonable time (about 30 minutes). I personally thought this a bit ironic, as if anyone were to have volunteered to be bumped onto the next flight in exchange for the discount off voucher, they would still have landed in about the same time.

My last flight with NorthWest then followed a number of weeks later. From Detroit back to the UK, I found the flight to be better than my outward journey. Probably aided by knowing it's length before hand, and the tailwinds, I found it started and ended much sooner. It may not have been an illusion though as we actually arrived early (the Captain made a point of telling us).
On screen, apart from the movies, I could see where the plane was during the flight and details of its speed. To my surprise we flew over Southern Ireland (near Cork) and then down to the South of the UK. This part being indirect. What the actual surprise was that this indirect route then took us over, the area I live and my house. From then it took 10 minute to reach Gatwick and land - I then got the train back which took me 2 hours! I arrived back after 6 weeks not wanting to be back, but regarding the airline as comfortable.