I live in downtown TO, but buy all my gear from two places - already discussed Dive Tech and Northern Tech Diver.
I also get some stuff at Dan's in St. Cathrines when time is an essence - i can make it there in under an hr
I also believe that the stores that are good for me will not be so good for other people, so someone asking for a LDS recommendation should always take it with a grain of salt
Back when i was diving single tank with a BC (not doubles with backplate/wing) i spent every weekend at Scuba2000 - talk all you want about Alec's self promotion on this board, but his customer service is outstanding and he does have a good selection on rec gear and you can try whatever you are buying in his pool to see how it fits - and return it with no questions asked.
They also have a DM or instructor leading the w/e dive at some local location - they were the once who introduced me to Great Lakes diving - and that's what the good LDS is supposed to be IMHO. Something much more than just then the place to buy you stuff
Time flies, however, and S2K does not have the toys i am after these days and both of Dive Teck and Northern Tech do. Northern Tech had a dive club as well, and i like diving with the like minded group of people - so those two are my "good shops" now.
Vlada