I recently had some time in Germany and was close enough to the Green Hell to pay it a visit. It fulfilled a lifelong dream to see and drive the track. The facility is incredibly cool, in a surreal German no speed limit autobahn sort of way. The fact that this track exists and is open to anyone that wants drive anything on it, is bizarre.
The day I went was not very crowded. There was easy parking right by the entrance with lots of interesting German hardware present. The usual suspects were there - various Porsches and BMWs and a few high-end Audis (RS5 Avant... wow). Surprisingly to me, there were a few Corvettes including a new Z06. And I got passed by a Challenger SRT of all things! I was driving a rental A3, manual, so I got passed by everything.