I really like Ofice 2007. But I realize it's a big upgrade, and some people may not want to install it yet. So what can you do if most of the people you work with are still running Office 2003? Simple! Point them at the Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats.
If you want more details about what the Compatibility Pack gives you, read this Knowledge Base article.