This may seem like a minor improvement but would certainly help lot of Google Docs users who frequently exchange spreadsheets with people who use Microsoft Office 2007.
If a person on the other side sends you a spreadsheet saved in the newer Excel 2007 format, you neither have to ask him for a previous xls version nor do you need to upload that "sensitive" data on to a third-party website for online conversion.
That’s because you can now upload Excel 2007 files (saved as xlsx) into Google Docs and it will import all cell data and formulas though the formatting was not preserved as you can notice from the above screenshot.
XLSX is the only format currently supported by Google Docs. You still need the help of other services for converting Word & PowerPoint 2007 files in a format that Google Docs can understand. Even Gmail can process Office 2007 files.
Related: Open XLSX Files Without Excel 2007