Microsoft has released a help document which contains information to consider when you plan a migration to Microsoft Excel 2010 from an earlier version of Excel.
Microsoft Excel 2010 is a robust program that differs in both appearance and function from earlier versions. With the ECMA/ISO Office Open XML File Formats, Business Intelligence functionality, and enhanced visualization tools, the new Excel 2010 spreadsheet program provides a comprehensive set of tools that empowers users to create and format workbooks for analyzing and sharing information, leading to more informed decisions than ever before.
While these changes are designed to improve the performance and experience of the program, there will be times when users encounter compatibility issues while working with workbooks that are created in different versions of Excel.
This paper, Migrating to Microsoft Excel 2010, has been developed to aid in the migration process. Here you will find descriptions of the primary functional differences and how those variances might affect workbooks. This paper also explains some of the more common issues that may arise during migration and offers solutions where applicable.
Additional read at Microsoft Office.