So I posted this before and it was removed for being a duplicate of a post which someone was whining about lag. This is not a duplicate of that and is a report about something different than an individuals lag.

The optimization is great but for other servers and world configurations it leads to huge fps issues. Items like signs, item frames, and paintings do not "render out" anymore making them load more of these items causing fps issues. Servers with plot configurations suffer from this greatly since they are now loading in the item frames, signs, and paintings which were not previously loaded. Prior to the "optimization" these items would not be rendered by the client when the player stepped back about 20 blocks.

Suggested fix: revert the de-render to its previous state so all those items in the increased vicinity are not rendered causing lag.