Things are a bit slow around here as I'm moving to a new server. I've also been playing a bit of Diablo II. Several aspects warrant mention: the multiplayer implementation does some really nice mixing of client and server side functionality. It seems designed to be resistant to connectivity blips. There's an interesting diagnostic for connectivity issues -- the gravity test. Items dropped require server confirmation to hit the ground. It's *net-physics*.
From a cognitive perspective, there are a lot of animations whose speeds are controlled by the players status. Humans are very capable of picking up very small variances in animation rates and seems underutilized in non-game UIs.