Details have recently been published and released here regarding service pack 2 for Office 2007. The current expected release date for this is sometime between February and April 2009.
Some of the features being incorporated into SP2 are integrated support for saving to PDF, XPS and ODF file formats - all of which currently require separate free downloads today. There are also some bug fixes and performance improvements included in this release. Specific details are provided at the blog link above.
While there are some great improvements coming in SP2, I would not defer any planned SP1 deployments that are currently underway or planned. The recommended guidance continues to be to continue with any planned deployments of Office 2007 SP1 to enable users to take advantage of the new functionality and improvements that are currently available and shipped in the product. You can then apply SP2 on top of that after it is released.
Performance updates for Outlook 2007 were recently released. You can read more about these updates and