I have benefited greatly from the postings in this forum and would
like to offer some information in return. We have an application
developed in Excel 2003 with extensive VBA. We have developed a
utility to convert this application to Excel 2007 but ran into two
significant problems. These problems exist with SP1 installed (not
very impressive performance by Microsoft):

1) Excel 2007 crashes when the command ThisWorkbook.Close was
executed. This may not occur in simple workbooks but occurs in some
of our larger workbooks.
2) Excel 2007 would delete some cell names and then throw an error
when code called that cell name. This occurs in a consistent fashion
but we haven't fully worked out in what situations this occurs.

The solution to the first issue is to place the code to close the
workbook in a seperate code module and to call that code module with
a delay using Application.OnTime Now + TimeValue("00:00:1"),
CloseFile where the module CloseFile executes the code
ThisWorkbook.Close.

The solution to the second problem seems to be to specify the name of
the worksheet when naming cells e.g. if you have a cell
named "MarketSize" on a sheet named "Forecast", then name the
cell "'Forecast'!MarketSize". Excel 2007 no longer deletes this entry
and the code will execute without errors.