Since 1997, the de facto standard format for office documents has been the MS Office format: .doc for documents, .xls for spreadsheets, .ppt for presentations, etc. ALL of the major non-Microsoft software of which I'm aware recognizes that format. That includes suites such as OpenOffice and PerfectOffice and stand-alone apps such as Abiword.
Set that as your standard and set all software to use that format. Tell your customers and clients that you are sticking with the existing MS Office format and not going to the MS docx. You might be surprised at who (and how many) say "Thank you!"
And if you need to review .docx or .xlsx files, OpenOffice 3 recognizes those formats or you can use the Office 2003 viewers along with the compatibility pack (
http://www.microsoft.com/downloads/details.aspx?FamilyId=941B3470-3AE9-4AEE-8F43-C6BB74CD1466&displaylang=en).
Please understand, I am not advocating that users be allowed to select their office suite. That choice, as with the choice of desktop operating system, should not be in their hands.
For me, it's a cost thing: Why buy software licenses when that money could be better spent elsewhere? A single license, with Software Assurance, for MS Office 2007
without media costs $289 at Newegg, $290 at CDW, and $297 at Tiger Direct. Let's assume a bulk discount of about 50% that knocks the license cost down to $145. Another poster mentioned 8,000 users. At $145/license, 8,000 licenses for Office 2K7 Pro is a $1.16 million expense. Knocking that back by even half is a significant saving.
