I spent 3 or 4 days in Buffalo a couple of autumns ago, ahead of a conference I had to attend in Toronto. I enjoyed it and will be returning.

There's a nice wildlife sanctuary/nature preserve near the river that I enjoyed, and the architecture is great. A day trip up to Fort Niagara is also worthwhile and not very far.

On the Canadian side are the better views of Niagara Falls, plus gorgeous Niagara-on-the-Lake.

Be sure to try real buffalo wings... two of the best places in the world to have them are in Buffalo.