I have a friend who has four kids. From April this year she's at home with just her youngest boy so I thought she might appreciate trading sitting sometimes, to have some time to herself. Today she finally took me up on the offer and went to her scrapbooking class. I looked after my Little Guy and hers for about two hours.
I felt quite nervous, I haven't looked after young kids before (apart from my own). Luckily it mostly went off without a hitch. My Little Guy was a bit territorial at first but soon relaxed and started sharing. He did hit our visitor once and made him cry but he realized immediately that it was wrong. Our visitor wasn't perturbed actually. I guess that's all part of coming from a large family.
Biggie was home alone with me until he was four and a half. We didn't have any friends to play with and he never went to a sitter, not even his grandparents. He is still quite shy in social situations. I think Little Guy will be better adjusted since we know so many people now. He certainly doesn't seem to feel the "separation anxiety" that Biggie did!