It was life changing. I did not realize how little rest in was getting when I slept until I started using it.
It took a few months for my pulmonologist to get the settings right so that it was fully effective. And having the mask on my face took some time to get used to. I use a full cushion that covers my mouth and nose.
One way that I could tell that iv was sleeping better was that I started remembering my dreams again. The sleep apnea did not allow me to get to deep sleep.
I was one who never had trouble waking up in the morning, but a couple years before I got my CPAP I noticed that in the morning I can started having a terrible just trying to wake up and felt so groggy in the morning. I'm now back to waking up more easily and feeling rejuvenated.