So I've been using it for 2 nights....I'm waking up in the middle of the night with my mouth wide open & totally dried out.  I've never been a mouth breather - and didn't breath through my mouth during my 2nd sleep study using the CPAP....what's up with that - is it part of getting used to this thing?

Yes, it is part of getting used to it. It took me almost a month to sleep correctly with the CPAP.

Thanks for getting back to me.  I'm taking it 1 not so enjoyable night at a time.  UGH!

I found that it was easier to get used to it by lying down as if for a nap and using it in short spurts. The eventually I workede up to longer nights without taking it off in the middle of the night.

It's actually gotten a little better.  I'm staying asleep for longer and when I do wake up its not for a dryed out mouth.  YAY for that! 

 You can get a strap for you chin to keep you mouth closed if you still find you are having problems.   It worked for me.   I did not feel beautiful - but I did sleep better.  ;-)