We just used Kids Nite Out for our ten month old twins. In our case, we had to have two sitters because the babies aren't walking yet, but they offered to find (and did) a sitter who would care for both. At first I thought that was great, but then I remembered that even I get tired at the end of the day taking care of two babies, so we went with two sitters so that each baby would have a caretaker. It was very expensive, $14 an hour for both babies, but worth it. Our sitters were long-time friends, one in college the other a law student. Both were friendly and professional and the babies did just fine.
From now on, babysitting services will be factored into the budget when we travel. It worked out really well.