All of the APIs documented in the Nintex Workflow 2007 SDK will be supported in Nintex Workflow 2010. Some API’s have been marked as obsolete and replaced. When the NW 2010 SDK is released it is recommended you move to the new API’s. SharePoint 2010 brings with it a new style look and feel.
Consequently, Nintex Workflow 2010 has been restyled to match SharePoint 2010. Custom workflow actions developed for NW 2007 will still have the SharePoint 2007 look and feel. These will need to be updated to utilise new NW 2010 style elements.