I got to see several R1Ts at the First Mile event at the factory back in October. I was very impressed with it. It felt like a finished product, not a prototype. I did not get to drive one, but I did ride in the back seat while an employee took us up and down Mt. Rivian.
My dad has had two Suburbans that allow the rear glass to open without the rest of the hatch being open, which was handy. For example, when we were in the pits on a race weekend and wanted to grab something out of the cooler, it could be done without running the risk other things falling out of...
When I was there on October 1, the employee lot was absolutely packed and people were coming and going. I was surprised to see so many people but it was really encouraging!