I have been living at Columbus Plaza for a little less than a year. My experience here has been great.
Pros:
Great location - Very safe and convenient to everything. Walking distance to Michigan ave, Millennium Park, Lake shore, etc.
Extremely helpful staff - All I needed to do if I have anything to fix in my room is to make a call or request a maintenance online. In 1 or 2 days the job would be done perfectly when I came back from work.
Nice property manager - I enjoyed dealing with the property manager in this building. Being very considerate, they are able to respond my requests promptly, and prorate my lease for a couple of days after the original date in my contract.
The convertible unit I rent is priced similarly to the studio units in the market, but is much more spacious as far as I'm concerned.
The 48th floor is lovely. Gym, sun room, and you can always use the printer and coffee machine for free in the computer room.
Cons:
Occasionally I could hear the sound from the fire station across the street at night, but I didn't find that too big of a problem.
If I weren't have to relocate due to job change, I would certainly continue my rent at Columbus Plaza. I would recommend it to anyone who's looking for an apartment in downtown Chicago area.