I also think the FS Marriott on Michigan Ave is pretty awful. The last time I was there, I couldn't check in until nearly 6:00 (as a platinum), the first room was awful (nice view) so they moved us to a much smaller room (though at least the water and TV worked). Their location is about all they have in their favor.
I recently stayed at the Hotel Chicago Downtown, Autograph Collection, and I liked it MUCH more than the Magnificent Mile property. I was upgraded to a very large room/suite, everything worked in the room, lounge was small but pretty empty, nice staff, good location. That's my new go to place when I have to go to Chicago.