I have stayed at the Chelsea almost exclusively over the last 20 years. It is not that noisy on the interior. There is the street noise on the lower floors, but this is common in all inner-city hotels in Toronto. The upper floors don't have it as much.
The services and amenities are on par with the other chains in Toronto.
It is definetly busy, with over 1800 rooms. Weekends are more chaotic, as many tour groups use it. Mid-week is still alot of business people. Most major airlines also use it for their crews.
Great location, theatre shopping and dining all walkable. Streets are safeer than most large cites, especially US.