I am primarily a side-sleeper, and I have been diagnosed with mild-to-moderate sleep apnea. I cannot tolerate C-pap and have been looking for other ways to cope with this. This is the only pillow actually approved by officialdom for use in treating sleep apnea, so I decided to try it. I have had it for several weeks now. I agree with other reviewers that it has to be broken in as the instructions also state. This took less than a week in my case. As I've gotten older (60), I have had increasing trouble deciding where to put my lower arm when on my side. This pillow has the solution built in! I will note that I am pretty flexible and have practiced yoga about once a week on average for decades. Maybe that has helped my shoulders retain good range of motion, but I have not had the difficulty with the arm placement required by this pillow that some other reviewers have noted. I do seem to be waking up a little less often, and my wake ups seem to occur when I have rolled over onto my back while sleeping. The pillow can encourage you to stay on your side, but, obviously, it cannot force a side-lying position. All-in-all, I would say it is helpful to me, and I find it as comfortable as any other pillow I have ever used. I think it will probably be a good partial solution for me.