We were taught in acupuncture school that this is the best point for nausea, and indeed, it is effective. For anyone who has suffered from sea sickness, you might have run across something called "sea bands" - elastic bands that are worn around the wrist with a small plastic disc on them. The band is to be worn so that the disc is right on Pericardium 6, thus stimulating this point. I've had more than one person report that it works.
But traditionally this point is used for more than nausea and vomiting. It can also be used for anxiety, or any sensation of fullness in the chest, as it helps blood flow in the chest - especially when there is also some kind of abdominal pain.
You don't need to buy sea bands, either. You can simply stimulate this point with your fingers. Don't be afraid to apply pressure - you're not going to hurt yourself. All you have to lose is the anxiety and or nausea. Knowing the right points to use can come in handy!