I hope the traffic logic gets an improvement. I remember having a lot of weird behavior with lane changes where every car would decide to change lanes at on specific spot on the road and line up to get to that spot.
Looking forward to see what else they'll be improving on.
Also a Plex lifetime user. I tried jellyfin not too long ago to see what the fuss was all about. I had heard that they handled her tonemapping better.
The interface is different but more or less just as good as Plex. It's definitely more for the person that likes to dive in the details of the config of their server. For example, you need to setup your own domain for external users to connect to. It's not done automatically like on Plex.
The focus on your content vs the "free" content Plex shoves in our face is nice I must admit.
Just a question of preference. In the end I stuck it out with Plex... For now.