I sweat where the mask contacts my face, so that's one issue. As others have said, it can be noisy. I find the noise highly variable based on how it sits on my face and if there are things (a pillow, a sheet, my hand) in front of the discharge vent. At times it feels claustrophobic. I feel vastly better in the morning if I've used the device for more than half the night, so I'm very motivated to make it work.