There's also a bug causing dwarves to not respect assigned beds when choosing where to sleep. Generally it doesn't make a huge difference, but when you get nobles showing up (who have preferences about how fancy their bedrooms need to be), they can become unhappy about sleeping in an inferior room, even though they chose to sleep there.
Edit: per the changelog, this bug has now been fixed for the next release. You may have to remove old beds and make new ones though, as there were some issues that weren't fixable by just having the new version update the save.