I've used the Oracle...or tried to, many times. Biggest problem and surest "waker-upper" I had with it was from snorting nose air leaks. The little nose plugs they send with it were very uncomfortable since I had to wedge them up very firmly into my nostrils to hold back air leaks through the snout. I even bought more comfy nose plugs - still were a pain to use. Depending on how forceful the nose air leaks are, most plugs will shoot right out eventually. Even if the plugs stay put, the periodic snorting feeling up in the nose was disruptive to sleep.
Mouth gets extremely (and I mean EXTREMELY) dry, even with heated humidifier and a heated hose. The flaps worn inside and outside the lips may or may not control mouth air leaks, which are usually accompanied by odd sounds. If dialed in snugly enough to prevent mouth air leaks, the tugging and/or vise-like feeling on the lips grew more and more uncomfortable as the night wore on.
The nub they left inside when they cut off the original wayyyy too long so-called "tongue guide" during their revision a year or two ago was still an unnecessary aggravation just inside the mouth. Front teeth bump it. Can't let jaw relax enough.
The drooling that many experience for quite some time with the Oracle was not a concern to me. I just kept a towel under my face.
Other than all that, it's a neat concept.

Just wish it had worked for me. Might work fine for others. The Oracle made me appreciate my ResMed Ultra Mirage FF mask.