We've used airbnb over the past few years, all good experiences (but not always a cheap option!). Prior to that we've rented houses in France/Spain/Portugal at different times over the past years too for a week or two at a time.
People renting out these places can be very careless. What I've encountered:
- We're in Lisbon for a few days right now, and noticed the airbnb owner has left a VERY VERY large amount of money in a jar in the kitchen.
- Was in Cork in Ireland at Easter and Hitachi vibrator (womanizer?) was in cupboard with the kitchen utensils
- Last summer in Brittany, what I suspect was fairly large bag of cannabis was in clothes closet
I guess these things are part of the experience :) (No, I didn't avail of any of them).