The only real issue I've seen with Jellyfin has been some stuttering on older clients (specifically, very old and crappy webOS TVs). I'm not sure whether this is a weak hardware problem, a network problem, or something else. Other than that, it's been very smooth.

(Context: I was a Plex user and self-hoster for about 7 years, and switched to self-hosted Jellyfin about 2 years ago.)