I honestly thought sleeping with the halo was going to be a much bigger deal than it has been. Once she made it through the first few days in the hospital (where she was in a lot of pain to begin with), she has been totally fine. She can sleep on her back or her side, and doesn't seem bothered by it at all. I never put it in her head that it could be uncomfortable, so she just learned how to adapt!
Some have said that with a regular pinned halo, it is most comfortable to sleep in a recliner (or in a bed where the head can be raised). I was prepared to have Abby sleep in our recliner in the living room if needed (thereby causing me to sleep on the couch!), but it hasn't been an issue at all. She sleeps in her bed with just one pillow, just like always. She seems very comfortable!