I adapted much more easily than I expected ... I had planned to really resist using it, but found to my amazement that I could sleep just fine with it.
HOWEVER, I am still struggling 7 months later to get a good fit on a mask. The RT who delivered it said "there is always some leakage of air with full-face masks," so I accept that, but think the fit should be better than what I have.
I do feel better in the day when I use it all night long, but haven't had the big pay-off some people experience in extra energy, etc.
My big problem is the sore on the bridge of the nose, where the gel ends. I ordered a "total face" mask that fits across the forehead, down the cheeks and under the lips, and it is wonderful ... such an improvement! ... but I can't get a good seal on it, either. I think this mask would be hard for people with claustrophobia, but it works for me, and lets me read while wearing it.
My second big problem is when I wake up during the night to go to the bathroom or because the mask has shifted, and I'm too sleepy to fuss with getting it back on, so I don't get the full-night effect.
To sum up, I can sleep OK with or without it, but feel better during the day if I've worn it all night. I think it's worth the struggle to adapt.