The rail service from Dearborn to Chicago is supposed to be about 5 hours, it seems longer. I remember hearing about buying right of ways to prevent freight train delays. that was about 6 or 7 years ago and I don't think much has changed. You do save on parking if you're staying downtown, but taxi fares and metro fares, combined with possible rental car fares seem to make it inconvenient sometimes.
About 25 years ago my son and I took Amtrak from Chicago to Clifton Forge, Va. There was no service into Roanoke, a town that once the lifeline of Norfolk and Western. It was hell. About 14 hours on the train, not to mention the hour drive family had to make to pick us up and drop us off.