Hi Gene,
The Beta 2 and B2TR releases both support the increased number of rows and
columns, but only on spreadsheets that are saved in one of the new file
formats (XLSX, XLSM, XLSB, etc.) If you save/open the file in the old XLS
format, you are in what's called "Compatibility Mode" which limits you to
the smaller sized sheets.
Cheers,
Dan
Excel Team