We have used them quite a bit as well as Craigslist. All experiences have been excellent save my wifes bachelorette party, that was C Plus at best, that was mainly due to a crappy landlord and poor communication about the hot tub. Jen did end up getting a significant chunk of change back from VRBO though so it was all good in the end.
We have a trip to Ireland booked next month and its 100% AirBNB, all cheaper than a hotel room and right in the thick of the metro area. Really looking forward to that. Also had an excellent rental in Tucson, super nice place, huge, right in the nice northeast corner of town, ended up being like $130/night out the door.
So yeah, do it. Way better than a hotel.