I'm running the new 4.4.0 and I'm unable to both be logged in and view the mapped domain on the front-end. I can navigate the admin via the original (sub)domain but as soon as I "Visit Site" I'm no longer logged in.
My Domain Mapping settings:
My wp-config.php file:
If I use the new exclude feature on a specific page, I'll continue to be logged in when I view the front-end of that page (it doesn't matter if I toggle the Force SSL setting, I'll be logged in when I view the original domain be it https or http).