Maid of the Mist, It was always something I wanted to do but never did. I thought hmmm tourists, probably expensive... etc. But it was totally worth it for the $20.
Keeping this review short and sweet, you should go. It's worth it on a mid week day. Maybe not on a weekend.
Fair warning: if you go to walk up the side of the falls, you will get SOAKED. Worth it.