I have used Airbnb for accommodation extensively, around the world....ok not all around the world, but in lots of places.
Most hosts were prompt with replies and the booking procedure was seamless.
One operator however, realised after a few messages that I was going to be travelling at a peak time for Australians visiting Turkey and put the price up by 3 times. I still had to go ahead with this booking very reluctantly because it was near impossible to find a place with four of us. Then the place was very difficult to find, and there was no hot water the second and third days.....no sun for solar heating. Very dissappointing.
On the other hand I booked an apartment in Paris, France for the Airbnb Open in 2015. The young lady was very helpful, met us at the metro station and was able to also assist when we had to change our train tickets to Brussels.
We have also used the service in Italy, Belgium, California, Australia, Germany, and found the hosts really good. We have booked rooms and apartments, the one in Los Angeles for the Open in 2016, was not up to scratch though.
I think it is a great way to travel and meet people, it's like turning up and you have a friend already.