If you want to know what images the term
"convention centre" turns up on Google (see link), you will realize why some, maybe most of us are heavily criticizing it.
http://www.google.ca/search?hl=en&gs_rn=...og&sa=N&tab=wi&ei=Hp5cUa-jNcKJiAKPuoHAAg
Also, the extension does not architecturally respond to or resemble the original building in any way. I really don't understand it, I think I actually prefer Atlantic Place to this building.