I have done twice out of pure desperation. One was an agency sitter, who was lovely (but my god they are expensive!). One was a friend's nanny. Both times they came and meet DS earlier in the week so he could spend some time with them first. I'm lucky in that DS is quite social and I think the personality of your son is something you might want to consider.
I had only good experiences, although the second sitter did go into my room (apparently she opened the door to let the heat in), and took out my dirty dishes to wash them up, which I found quite invasive and embarrassing.