There is a long detailed thread either here or in Stumble Inn about this subject.

I have used my C-pap for almost a year now. The new masks make it a lot better. By the time I am almost asleep I can hardly tell I have mine on. I sleep on either side or my back. I sleep in a super single water bed which is bigger than a twin but not as big as a full so the 8 feet of tubing give me a lot of moving room. I think with the C-pap on, it is actually impossible to snore, that was one of my problems. Anyway, i sleep much better.

When I was a nurse, the masks for the old fashioned C and Bi-paps scared me to death they were so big. I don't know how anyone slept with them.