If I join another player as a client in multiplayer, removing items from item frames does not work.

The client will see the item in the frame disappear, but the host sees no change at all. Clicking on the item frame again causes the old item to re-appear rotated.

Before 1.0.3, creative clients in multiplayer would send an ItemFrameDropItemPacket with an Air item to indicate item removal without drops. However, since 1.0.3 this packet is not sent at all for creative players, and on top of that, the item field has been removed from the packet altogether.

The information above was obtained while working with a custom server, and then used to reproduce the issue in vanilla.