Passed! Phew, what a ridiculous ride that was.
In case it helps someone: I started studying about 4 months before the exam, but I was very lazy about it until early January (I took it at the end of March, so this was ~3 months of really solid studying). I did all the UBP case stems twice. The first time through, I was mostly just reading the answers, but I answered them all out loud the second time through. I also read the little red book, "Rapid Review Anesthesiology Oral Boards," twice which I actually thought was really good. It was a good, concise companion to the absurdly verbose UBP answers. I also highly recommend the UBP OSCE add-on. It was really helpful to have lots of monitor/TTE/ultrasound references for the exam. I honestly don't think it taught me things I didn't know, but it was most helpful because it was presented in the same format as the actual OSCE stations. As you go through the UBP OSCE stuff, keep a print out of the ABA OSCE outline and make sure you go line-by-line so you don't miss anything.
I also worked through all of the available oral board stems that are available online (here's a good compilation:
http://www.physiciantravels.com/wp-content/uploads/2017/03/Mock_Oral_Exams_II.pdf) and did as many mock exams as I could with friends and other staff. After I did a bunch of UBP, I found this the most helpful. It helped me organize my thoughts, vocalize things in a concise manner, and my examiners were good about trying to trip me up, derail me, and get me off topic. I agree that this is both a knowledge exam and an endurance exam. By the time I got to the second stem, I was totally fried. But my prep, I think, did a good job of preparing me how to stay on task and think clearly about the basic things I needed to say to get through it. For the OSCE stuff, just remember that it's a game. Be empathetic, a good listener, tell them what they want to hear, etc. They want to make sure you're not a robot and you're capable of some basic reasoning and emotion.