Upgraded from 2.5.1 recently and have pretty bad problems:
1) Autosave. Need an option to disable it. It autosaves too often, even if I just saved manually.
2) A document often gets corrupted. Blocks of document get intermixed with inserted image tags.
3) I have some custom attributes that have ' in their names. Every time the document is saved, WP tries to escape them. So "Maxim's Rating" becomes "Maxim\'s Rating" after first auto-save, then "Maxim\\\s' Rating" and gets worse every time it's re-saved.
4) Plugin upgrades don't work. When there's a new version of plugin, I see the message that says "Download it here" or "Upgrade automatically". The automatic upgrade link renders nothing. All I get is the menu bar, but the plugin upgrade fails without any messages.