Niagara Falls is an amazing spectacle. Seen from the top, the bottom on the maid of the mist, the skywalk, the top of a hotel its all good! If you can, I recommend doing the boat - the Maid of the Mist - its a very different perspective on the falls and you get a much better sense of scale. Its also great to go at different times of the year - the boat is only possible from late May to Sept (I think) but seeing the colours of the trees in Autumn or the frozen section of the falls in winter are also truly magical. (and its quieter then!)
The downside is that unless you drive up and park near the falls you will be walking through the craziness that is the town of Niagara Falls. Arcades, fun houses, gift shops, laser quest etc etc. Don't get me wrong, its all good fun, but in contrast to the simplicity of such an amazing natural wonder its a fluorescent commercial shock!
If you want to keep it natural and chilled out my suggestion is to stay somewhere like Niagara on the lake or one of the nearby towns and then drive along the scenic parkway (see the butterfly park, the botanical gardens, the whirlpool etc) and up to the falls and then drive away again back to the quieter and quaint town of Niagara on the lake for dinner.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.