Earlier in the year we travelled from Palermo to Genoa with GNV.
Overall a pleasant experience, but the port experience is tailored for vehicles.
The ticket said to check in at the port, but having found the office, we were redirected back to the quayside, where there was no seating or shelter. The sailing has been delayed by a couple of hours, and the cafe opposite the port was closed, but we found a street with restaurants about 10 minutes away.
On arrival at Genoa, it was about 20 minutes' walk to our hotel near the station.
On boarding the cafeteria was open serving hot meals, but with the delayed departure I saw nobody eating.
The ferry was lightly loaded; only about a dozen foot passengers. There was always plenty of seating available in the lounge/cafe-bar. Cabin was comfortable.
The cafeteria remained closed during the day, but sandwiches and snacks were available. The website said credit card payment only on board, but as the machine was out of order, it turned out to be cash only!
The sea was very calm.
You can buy WiFi access on board, but we didn't bother. There was some internet access as we passed Corsica.
I'd recommend it as long as you don't mind standing around watching cars loading.
Feel free to ask any specific questions.
