Last night was the first full night of successful (?) CPAP use. I can't honestly say I noticed much of a difference in the quality of my sleep ... if only because I kept waking up from having a hose strapped to my face. For some inexplicable reason, I was getting water collecting in my mask, which was not exactly comfortable either. I barely have the humidification on ... I might have to leave that part turned off.
My deepest bout of sleep came after the alarm went off and I took off the mask. Take that for whatever it's worth. 
 I always seem to do my best sleeping after the alarm has gone off. I sometimes think about setting the alarm for 2 a.m. just for that purpose.