AirBnb generally works pretty well, or at least better than the rival offerings. I'm not sure about "tidy little earner", it is plenty of work and unless you are in a particularly desirable area not as lucrative as you might expect.
A few random thoughts:
If they offer a photographer, take it up.
The place has to be spotless, and has to have wifi. Make sure there are towels, bedding, shampoo, bog paper; everything else is optional.
Guests expect to be able to book late, and for short periods. Think about whether you can be bothered with one-night stays. They will book random dates, which leaves you with voids all over the place. If you only let for a minimum of a week expect only one booking a year.
AirBnb will hassle you constantly to reduce the price. Ignore it. If there really are "other hosts in your area getting bookings at £22/night" for a four bedroom property, that's their problem, they will soon learn or go bust.
Respond to enquiries within an hour, it affects future enquiries.
As for pitfalls, only the usual minor issues. Someone lost the remote. Someone clipped the wall with their car. Occasionally a guest will use every item of crockery and glassware and not wash up. Overall virtually everyone is pretty good, and no-one's tried to have a facebook party. Airbnb have insurance for that, but make sure you inform your own insurers too.