I seems to me to be no more than a subway in the air. Mass transit is needed for mass peoples. Less polution and better parking rates. On the other hand.... I wouldn't live in Seattle or a suburb thereof, if I got an annual check of $10,000 for doing so.
If you want real "Mass Transit" the answer are freeways. They cost less, move more people, move freight as well as people. And you get to sit in the privacy of your car, at the temperature you like, listening to the radio station of your choice without the homeless guy breathing on you.
You get to go directly from your house to your work without changing trains. Or make a stop at the store without having to wait on the next train/monorail in the Seattle rain or Phoenix sun at 115 Farenheit.
Any gripes about freeways can be fixed for less than any rail type of mass transit.
Even polution can be fixed 100% by hydrogen or electric power, and since polution has improved dramatically in the last couple of decades, it's not such a big deal anyway.
Trains and monorails are cool. But they belong in museums and Disneyland.