The rollback is truly something else. Although - and I may be crazy - I swear it isn't quite as good as playing local people with delay-based netplay (such that the network delay can "hide" behind the inherent lag of the Gamecube/game itself)
The fact that they were able to optimize two frames of input lag away to make the online gameplay have the same latency as offline is itself incredible.
As far as I know, even other rollback-equipped fighting games still add a little bit of latency in order to play online without requiring constant rollbacks.
That said, Melee is also a game that is very hard on the rollback, because movement and attack startup are far faster than in many fighting games.
Dashdancing with rollback leads to some annoying camera judder.
Depends on the ping. I would say once you start pushing 80 you can definitely feel it. But >60 ping rollback feels very good if you are playing on a good monitor.
In a way, Melee shows that a couple of artificial frames of lag can be beneficial and allow for seamless online play on-par with LAN. Since the game is already one of the fastest & most reaction-oriented out there.
But outside of that edge case, it's outstanding.