Years ago, I worked for Mesaba in FNT. This was during the Fokker F27 days (anybody remember those?) in the late eighties. These birds would break down all the time and FNT was usually an easy victim. If they had a broken bird in DTW, they would usually steal the plane for the DTW-FNT in order to protect Erie, Marquette or Dayton. We would get all the customers a $300 voucher and get them to DTW in a cab. I ended up going to Mesaba in MSP as an assistant dispatcher. I remember there was a dry-erase board in the dispatch office where need-to-know information was left for all dispatchers and it read in huge letter "DO NOT XLD FNT". Apparently, a customer got so fed up with all the cancellations that he ended up getting "The Flint Journal" involved and a couple of the local TV stations picked up on the story. Needless to say, the dispatch reliability for FNT was quite examplary, for a couple of months anyway ...
As far as the rental car, it makes sense for an airline to pay for one i.s.o. putting you up in the Westin for 2 days (which is just silly, because you could have walked home in 2 days ). However, as far as I know, NW never pays for a rental car because of liability reasons. What the agent should have done is tell you that NW will not pay for the rental car but offer you a TCV. I know this is what you ended up getting after you communicated with TTU but the agent should have taken care of this.