Used AirBnB year before last for Origins and it was nice using it again this year.
This will be the first year in almost a decade that I *haven't* used AirBNB for GenCon - and only because we only have four people going this year, and my housing lottery time was 12:01. ;)
That said, it's a fantastic service. In several years past, we've gathered a group and secured a house within a few miles of Downtown that ends up sleeping everyone comfortably (many with our own bedrooms), saving us some money on food, and typically ends up being pennies on the dollar per night (I think we've averaged somewhere around $40 per night per person over the years.) You end up with a fantastic place to hang out, play games, eat-drink, etc...that you just don't get with the hotels.
The trick, as with anything, is to look at the listing. Many people mention GenCon in their listings, and if you take the time to look into your hosts (as suggested, look for multiple reviews and good ratings, and preferred hosts in your search), I really believe you can't go wrong.
Used Airbnd last year and our first reservation was cancelled once the owner realized it was for Gencon. They then immediately raised their price. We found another the same day with no problem. Full house, multiple bedrooms, 3 bathrooms, and a hot tub. It was fantastic. Renting one this year for a smaller group but we still have separate bedrooms and 2 baths...for much cheaper than a hotel. Aside from Gencon, I use Airbnb for vacations all the time, and have never had a bad experience. Like a previous poster said, you just need to check out the reviews and have a few different options in mind.
I had a decent AirB&B experience last year, but then this year my friend booked a room for us in an area that ended up flooding the day before the reservation. The area the guest building was in was under a mandatory evacuation order. And AirB&B's best offer was a -partial- refund. For a room that was, I believe, literally filled with standing water at one point when we would have been staying there.
Yeah, not doing business with them anymore, needless to say, Gen-Con or otherwise.
For Gen Con, we are using it for our first time. One of group members booked it January 2018 for this Gen Con since we never manage to get good hotel lottery time for downtown rooms (out of 10 people...). So far, no cancellation and I am pretty excited to have the whole group under one roof AND we all get a bed.
Outside of Gen Con I use AirBNB/VRBO several times a year and love it. Usually much more comfortable and cheaper than hotels. Never had any issues at all.