Paul Andrew, Microsoft’s Windows Workflow Foundation Technical Product Manager, has the details:
We released Windows Workflow Foundation Beta 1.2 today [Nov. 4]. As described on the download page, this release is primarily as a pre-requisite for certain parts of Office “12″ beta 1. In terms of functionality there’s no difference between Beta 1 and Beta 1.2 but they require different versions of the .NET Framework.
Beta 1 was for .NET Framework 2 Beta 2, while 1.2 is for the final .NET Framework 2 released to manufacturing and launching on Monday with Visual Studio 2005.