Well for a start, the people. I found Canadians to be really friendly, similar to New Zealanders, and I met lots of cool tennis fans.
Then, access to top players. I'd never been to this event before and I strolled in on the Monday, walked over to the first court I came across. There was Federer practicing. He signed a bunch of stuff afterwards. Then I walked over to another court further down. Nadal practicing. I got to the front easily and watched, then he came over and signed stuff (see pic).
The weather was great, the layout of the place was nice, the main stadium is awesome, cool shopping for tennis gear, prices weren't too crazy. And then the city itself, I loved Toronto.