My office is upgrading from Excel 2003 to Excel 2010 and we have a lot of tools in Excel 2003 (complex custom formulas, named ranges, VBA, pivots... almost every feature of excel can be found in at least one of our tools).

What kind of problems could crop up? A lot of the stuff I've tried have worked perfectly, but I've heard that some VBA will no longer work and was wondering if there was a list somewhere of which VBA commands might cause problems after transitioning to 2010. I've been told that excel 2007 and excel 2010 are very compatible with each other, but the problem is a few of the excel 2003 things didn't make it to excel 2007 and thus not 2010, so a list of VBA that no longer works in 2007 might be just as helpful.