XLSB is binary format that should theoretically allow fast reading and writing to the file. 

With the current implementation, the Notes support only a rectangular shape.

Examples:

The button should always be active. 

The button:

When the Freeze Panes option is enabled and try to insert a new comment into the next cell on the left to the Freeze Panes separator the comment is deleted.

Add support for conditional formatting of cells - allow applying of rules used during visualization of cells to automatically apply formatting depending on their values.

Custom style is not applied to empty cells when applying to the entire row.

Workaround: 

Dim usedCellRange As CellRange = mobjValidationResultWs.UsedCellRange
For rowIndex As Integer = usedCellRange.FromIndex.RowIndex To usedCellRange.ToIndex.RowIndex
    For columnIndex As Integer = usedCellRange.FromIndex.ColumnIndex To usedCellRange.ToIndex.ColumnIndex
        Dim cell As CellSelection = mobjValidationResultWs.Cells(rowIndex, columnIndex)
        cell.SetStyleName("Common")

    Next columnIndex
Next rowIndex