Bukkit

1.4
/icmd now just places a command block in your hands.
/icmd related permissions are now applied when users edit the command block by right clicking.
Custom packet handling to allow editing command blocks without OP.
1.3
Fixed a bug where instances where not removed from a party when they are deleted, causing an exception when subsequently they were deleted again.
Added /ispawner create command to turn an Entity into a spawner.
Improved /ispawner command to instantly update the spawner rather than having to wait for it to spawn a monster.
Improved TileEntity writing code to cause the client to update immediately.
Fixed a bug where the plugin detected Multiverse-Inventories as present when it is not.
1.2
Fix bug where homes and spawn setting were sometimes lost on a server restart.
Added /icmd command for creating and editing command blocks, with ability to restrict command usage with permissions.
Cleaned up code for reading & writing TileEntity NBT data.
1.1
Allow setting the spawn world to none, to avoid conflicts with other plugins. Note: if a player is in an instance which gets deleted, they will be teleported to the first world's spawn point if there is no spawn world set.
Added support for setting gamemode, based on a third party worldmanager's gamemode setting for the world. Multiverse is the only supported world manager.
Rewrote instance loading code, no longer requires destination world to be loaded.
Instances no longer always spawn monsters, this setting should be correctly cloned from the destination world.
Instances have their own chunk generator which only generates empty chunks.
Fixed bug with instance unloading happening whilst players are in the instance.
Fixed bug with instance unloading never happening in some cases.
Instance difficulty is now a setting on the portalpair, defaults to difficulty of the destination world at creation time.
Optimized onPlayerMove to only perform checks when the player has crossed a block boundary.

Chunks for instances are stored entirely in memory.