Niagara Falls NY is a fairly quiet town, although in summer I expect it can be busier with all the various activites on offer in the National Park. However, for the best view of the falls head over the Rainbow Bridge (50c) inot Canada and have a look from Niagara Falls Ontario!
From here not only are the views beter, but there is more to do in the town, even if it is slightly tacky and theme park styled!
Also, ensure that you see the falls lit up at night, as well as, if possible, seeing them in the depths of winter when the river outlet freezes and huge chunks of ice cascade over the falls! Just don't expect anything on the USA side to be open!

Sto by the Canadian side and get a big steak dinner. Purchase it on your credit card and save big money as the exchange works.

If your planning to visit Niagara, its always better to get a Canadian visa (if you have right papers, you can get it in 2-3 hours from the consulate in Buffalo). Imagine waking up to the view of Niagara falls, thats only possible from the Canadian side. I stayed in Sheraton on the US side and ended up paying around 200$ per day and the same room (overlooking the falls ) in Canada side was just around 50-60$. Its not just about the money, also the view of the falls and experience is much better from the other side.