I will go first. MIL ain't as bad (as say BIL, who's feeling lonely and barges into our bedroom over the holidays while DH and I are already in bed, together) - not terrible bc she's a proud lady who wants to keep up appearances.
Once I got sick but still wanted to travel for the holidays bc DH and I were in school and doing long distance and the holidays were a rare oppty to be together. When I told my in laws I was still going to come but take meds, she emailed my mom and told her she felt sorry I couldn't come that year but none of her family or holiday guests could afford to catch anything from me. My mom was livid and booked me a flight to my childhood home instead (DH was studying there too), and DH stayed with me some of that time (he cancelled his flight home to please me, but didn't visit me every day to please MIL). I was mad that he didn't side completely with his wife, but at least he made sure to cancel his flight home.