In 2003 I worked for the fixed wing operator there that did the tours out of CYSN. Our office was right next door to one of the helicopter operators. We were in a constant battle with them to get business. The summer I worked there tourism was down and we were not very busy and either was our competition.
All the pilots (5 of us) were laid off for the winter which was the norm at this business, and same with the helicopter company. However the owner there was also a pilot and was pretty much on call during the winter just in case they got a walk in or a bus of tourists.
Now there is another operator where they have their own heli-pad very close to the actual falls. I believe he has a special permit where he is able to get quite close and fly quite low to the falls. There is restricted airspace due to the Niagara Falls Air Force base in the U.S. This operator is very successful and has been around for a long time. But again its seasonal work, I believe they are very busy in the summer and slow down in the winter. They also offer winery tours of Niagara and actually do some work for wineries in the area. This company is called Niagara Helicopters.
Now from my experience when I worked for the fixed wing operator they weren't making much money. But back in the day when tourism was high and fuel was cheaper they were doing ok. Throw in high fuel prices, bad economy and swine flu or the like and the business is going to suffer like any other tourism based operation. But Niagara Helicopters have seem to beat the odds and done very well.