You're correct, however, we tried exporting our charts in each of the formats
supported by Excel 2007 (png, gif, and jpg) and jpg showed the best results
in all but this one instance.

We even tried wmf, which you can achieve by copying and pasting the chart
from Excel into Word. When you open the .docx file in WinZip, you'll see the
image has been converted to a .wmf file.

You're also correct that previous versions of Excel did a better job at
picture fidelity.

Perhaps I should give a more complete picture of what we're doing. We have
an in-house developed Excel Addin that we use to create a bunch of standard
charts. We then import those charts into a Word document using a Word
Template with VBA code. The VBA code fires up Excel and asks Excel to export
each chart as a jpg, then it imports the jpg into the Word document.

Before upgrading to Office 2007, we used to simply do a copy/paste operation
in our VBA code, but we found that the image quality was really poor. So we
switched to exporting the images. And as I said, we found that jpg looked
the best in all but this one chart type.