Microsoft has just released an update ((kb980028) for Office 2010 beta which contains stability and performance improvements for Word 2010 (both 32 and 64bits).

This update also fixes a problem in Outlook 2010 Beta in which the size of an e-mail message is unexpectedly large.

If you are a Microsoft Office 2010 (beta) user, it is recommended to install this updates for better performance and stability.

Remember that the update is available only for Microsoft Office 2010 Beta and not for Office 2010 RC version.
More information and download at source