UPDATE 3/18/21 I've got over 80 hours on this game and am maybe half way through the story and playing side quests, which are great by themselves.
This game may not live up to the pre-release hype, but it is still incredible. I'm playing on Stadia via Chromecast Ultra with 100Mbps down and 10Mbps up internet speeds and am very pleased with the game's performance. It is gorgeous. Night City is jaw dropping. Vehicle and pedestrian traffic, however, are underwhelming and detract markedly from the immersion. Aside from being sparse and buggy, the NPC models lack variety and you often see duplicates wandering in the same vicinity as one another. The vehicle A.I. is very primitive and unrealistic. Furthermore, as others have noted, vehicles appear and disappear outside of your field of view in a way that is very unrealistic and kills the immersion. For what is supposed to be a thriving futuristic urban environment the scant number of vehicles on the streets makes it feel more like North Korea than Tokyo. Otherwise, the city scape is very diverse and interesting to explore. The main character NPCs are pretty detailed, but it's like the devs screwed up the Euler angles for the movement of props like cigarettes and cell phones that tend to flip and translate in mid air around the characters instead of tracking the movements of their hands. Regardless of these bugs and distractions, the game is extremely fun to play! The voice acting is decent, and the main story and side missions are engaging and interesting. Character customization is sufficiently deep. And weapons and items are diverse and exciting to find, use, and customize. Vehicle handling is arcade-y, but not all that bad. I do wish vehicles could be modded and upgraded and would require fuel. I keep complaining, but I really do love this game and its potential is limitless. CDPR has created a great foundation. I hope they continue to refine it and create the game that they set out to create.