I haven't read anything about the removal of the mime information for pages in Opera 9.2. As my page can be served as several different mime types I'd like to know how to re-enable this feature if it is possible.
This information is now only available in the Info panel. Press F4 to enable the sidebar, then select the Info panel while your page is active. It was removed from the tab tooltips as it was confusing information for most users.