Compared to all the other outdoor rinks I know of in downtown Toronto (okay fine so I only know of this one and Nathan Phillips) the rink at the Harbourfront Centre is about 10,000 times better. The large size and the non oval shape of the rink allows for a much better time skating.
The other big plus is the music they play and the live DJ's they have that spin at the rink on certain nights! I spent an hour and a half skating here which is something I haven't done since I used to play hockey!
The have pretty crappy skates for rent unfortunately so it's better you bring your own but otherwise this is a great place to go skating.