It replaces TCP+TLS, and runs multiple streams on the same conn, supports transition from eg wifi to ethernet on at least one of the nodes. And since it's over

It replaces TCP+TLS, and runs multiple streams on the same conn, supports transition from eg wifi to ethernet on at least one of the nodes. And since it's over udp implementations are mostly in user space. Which is good if you want it now, but not great for performance. Ip packets are very small so you gotta have either kernel support for quic or batch IO, otherwise it's often CPU limited (yes, really). In addition congestion control is wonky, unfortunately. In my experience (quic-go), it's too shy in the presence of TCP streams, which ends up getting more bandwidth. But that depends on the algorithm used, implementation and God knows what else.