Using a metal filter and springs transformed my experience
Every single guide should point out how important this is!
I've had my ORB for a few days and was unable to get a decent coffee, as everything was extremely acidic. It was a very frustrating experience at first, as I went from a Nordic roast to a medium-light roast. Nothing tasted nice.
I then realized that the puck was swelling during the pre-infusion, as the CO2 was expanding between the ground coffee particles. The only solution that completely solved this was an Aeropress metal filter and two shaker springs, which forced the puck to remain compressed.
If you can't get something nice from this brewer, definitely try this.