First night it was a dream come true - never slept that well. Also took my first ever Allegra D that night - best I had ever been able to breath.

Still makes a big difference, but not as dramatic AND there are nights it bothers the hell out of me. One night trips I leave it at home, two or more, I take it with me.

Try numerous masks/nose pillows find what is comfortable.

If using nose pillows make sure your mouth stays closed during sleep, I initially even had a chin strap to remedy this, but now keep my mouth shut.

Make sure machine has a "Ramp up" feature. When I first put mask on it is very low pressure, barely noticeable so not uncomfortable - over next 30 mins pressure increases and usually I'm asleep and don't notice. If I wake up in middle of night, I hit the ramp up feature and it's a lot more bearable.

There are some nights, for whatever reason, that it is just uncomfortable and I give up and take it off - even after over 10 years.