As far as food and service are concerned, this is definitely a must-try in Toronto. I have only good things to say about Diana's.
The gentleman working the oyster bar was knowledgeable and gave excellent recommendations. He suggested 3-4 oysters and was spot on with what we were looking for. He shucked an oyster for me to try before we ordered. We had seconds, of course!
Our waiter suggested a great wine, and checked on us just the right amount to be thorough, but not pushy or hovering. In fact, some of the best service I have had I years! I didn't eat my dessert, and he removed it from the bill even though I said I was full, and not because I didn't like it.
Our entrees were also great. I had salmon and my husband had the NY Strip.
The atmosphere was a bit noisy--not relaxing or romantic, but as it was a Saturday night, it was hopping! Lots of large groups.
Will definitely be back. Wish I remembered the server's name, because I would like to commend him too.