In addition to the total incompatibility with Office 2004, Microsoft have identified numerous issues with 2008 and 2011. You can expect that Microsoft will release an update within the next couple of weeks.
If you use Office extensively for work, you may wish to bear these things in mind before upgrading!
Microsoft has been working with Apple from the early days of MacOS 10.7 (Lion). Through this partnership, many issues were addressed leading up to the Lion release. Microsoft will continue to work closely with Apple to address problems that may occur with Office for Mac 2008 and 2011 and Lion OS.