Do you participate in a babysitting swap? How does it work?

I'm doing a babysitting swap with neighbors for the first time tonight. I came over at 7 put their kid to bed and will watch TV (or work) until 11 or so. As soon as we can pick another mutually agreeable date DH and I will get our turn to go out.

A friend's neighborhood does it where all the kids (6-8 of them) stay at one house and all the parents go out, often as a group. DS is not yet 2 so he seems a little young for that but I look forward to trying that in the future.