This looks like a great addition to Michigan Ave. I will echo the concerns of others about the blocked views of the Allerton Hotel, and the loss of a handsome limestone building. If the alderman pushed back on this at all, it should be to see if it would be feasible for the developer to reuse the limestone facade.
All that said, this will add a large number of new residents to the area and help with the vibrancy of the neighborhood. Build it, and please silence all crybaby NIMBYs out there with extreme prejudice