There are several items that currently cannot be localized:
The headers and the description of the items have hardcoded strings.
When importing a document containing a hyperlink formula (e.g. "=HYPERLINK(B2,A2)") an exception is thrown: System.Collections.Generic.KeyNotFoundException: 'The given key was not present in the dictionary.'
The WorkbookContentChanged event is invoked right after importing a document.
The scale factor is not imported from documents with no information about the selection state.
The outline properties of the chart series are not respected by most charts.
Setting up a paper size to A1 and exporting it actually sets the paperSize to 1. Using the same scenario in Excel sets the paperSize to 305.
This leads to inappropriate values when entering the Page Setup options later in Excel.