Yes, there is one known issue with three possible resolutions. Microsoft has changed the default behaviour of looping actions in SharePoint 2010. Any Nintex workflows that use the “Loop”, “For Each”, or “State Machine” actions will be affected.
The affected actions were refactored in build 11002 (Dec 09) according to advice from Microsoft. Any workflows created or re-published using this build or later will work correctly in SharePoint 2010.
Depending on particular circumstances, there are three options for dealing with older version workflows.
Option 1: Re-publish any affected workflows using Nintex Workflow 2007 build number 11002 or higher.
Option 2: Re-publish the affected workflows using Nintex Workflow 2010.
Option 3: Edit the SharePoint 2010 web.config file to revert back to the 2007 SharePoint behaviour.
A full explanation of this issue, and decision criteria / implications will be documented in the upgrade guide.