Entity activation / tracking ranges to control when entities are ticked / sent to the client.
Configuration of some hardcoded messages and variables
Anti XRay
Support for BungeeCord IP forwarding (a la X-Forwarded-For)
Many (130+) other minor performance and bug fixes.
Plugins should be developed against the Bukkit API, but Spigot is recommended as the server platform unless you require bug for bug / 99% compatability with Vanilla gameplay.
Spigot API Additions - https://hub.spigotmc.org/stash/projects/SPIGOT/repos/spigot/browse/Bukkit-Patches
Spigot Additions - https://hub.spigotmc.org/stash/projects/SPIGOT/repos/spigot/browse/CraftBukkit-Patches
Plugins should be developed against the Bukkit API, but Spigot is recommended as the server platform unless you require bug for bug / 99% compatability with Vanilla gameplay.