My Mom, Dad and husband use them. Which of course probably means that I should get tested. There are not any drawbacks that I can see. I may take some adjusting to using the machine but everyone feels better. My mom had a heart attack each year until she started using one and has not had any problems since. That certainly points toward an oxygen deficit on her part prior. The new machines are very quiet. DH started using one prior to the "new machines" and even at that I could easily imagine the sound as wind in the trees or waves on the beach and it did not bother me.
DH had some difficulty when he used just the nose mask because he would breath in through his nose and out through his mask. This manifested itself in my wild giggles in the middle of the night as he sounded so darned cute. He now uses a full face mask and gets a much better result and I am sleeping through the night (hee hee).