What happened in the 4/5/2011 Team Fortress 2 update? [closed]

According to the wiki, here's what was found:

Undocumented changes

• Added the [ classified ]
• Updated Magnanimous Monarch texture file.
• Updated stock maps with AI movement information.
• Turned Quality of some Vintage Lugermorphs to Unique in player's backpacks.
• Changed levels of some items in player's backpacks.

The [ classified ] is really the Potato Hat. The file diff at the bottom of the page doesn't seem to reveal anything but the aforementioned changes (mainly the addition of the Potato Hat, the changes above were probably based on what was found in the diff).

There's a new post on the blog but it's merely an aggregation of some community updates.

So there must be some sort of surprise... or could it be the Potato Hat after all?