XenForo released 1.2 beta today.
A local installation of this site running XenForo 1.2 beta and XenScripts 1.3-alpha shows a minimal number of issues, however, this could change under strain.
Expect many add-ons and styles to be broken after upgrading to 1.2. You must test your add-ons thoroughly or look for updates. Be especially careful with add-ons that cover similar features to ones that are added to 1.2; these may conflict with the core XenForo data. If data conflicts are found, they will need to be resolved in a new add-on release or by removing the add-on before upgrading to 1.2.
A local installation of this site running XenForo 1.2 beta and XenScripts 1.3-alpha shows a minimal number of issues, however, this could change under strain.