I rent out the Granny flat on the side of my house through it. Guests tell me that their experiences have varied widely, depending on the countries they have visited, but in general North America seems to be ok as is western Europe, apart from Greece and Barcelona.
I use it more than hotels these days: it's particularly good if you're travelling as a family (compare price of 2 or 3 rooms in a 4* hotel) with the added security of having the whole place to yourself (if you wish): try getting several hotel rooms to be interconnected and it starts to get extremely expensive.
In the last 2 years of using it I've never had a bad experience. So far I've used it in the USA and 9 EU countries.