Ok, first the cons (please read past this part, it gets better): The neighborhood is a bit down in the dumps. The city went through a severe depression, and there are many vacant neighborhood houses with tall grass, boarded up windows, and occasional graffiti. If you're not used to this, it might be off-putting at first.
But don't let that scare you off. It's a normal neighborhood. I didn't see any evidence of danger or crime. The room is a 20 minute walk from the falls. I walked this multiple times and never felt any danger at all. The neighbors I encountered were friendly.
The room has been recently refurbished. All furniture, bedding, appliances, fixtures, and even the entire bathroom appear to have been newly installed (as of 8/2017). I liked the nicely polished hardwood floors. It's likely cleaner and much more comfortable than most of the hotels nearby. Added bonus: there is a big balcony just outside the room from which you can enjoy the Niagara Falls fireworks.
Our host was extremely friendly. He lives in the building and met us upon arrival. He helped us carry our bags and gave good advice about sightseeing and local restaurants.
Small advice: Upon booking, contact the host directly to confirm the address. The Airbnb provided address had a small typo.