I still think a large new hotel is needed (the couple hundred rooms proposed around the downtown are great (Alt on Slater (148), Re on Queen/Sparks(110), Hyatt(158) in the market), but they won't solve the Convention Centre's big problem which is accommodating it's guests in the fewest amount of hotels. When you look at the other big cities in Canada, their Convention facilities have exponentially more hotel rooms directly adjacent to their buildings. I recommend at least another 500 rooms over the old registry office. See link below (click the dots on the map, of the big 6, we only beat Calgary in adjacent hotel rooms);
http://www.conventioncentrescanada.com/members_centres/members_start.html
On another note, the OBJ article also talks about fixing up the skywalks, the Rideau and (as we have already seen) the Mack Bridge as well as connections to the subway.