More information: http://msdn.microsoft.com/en-us/devlabs/ee334183.aspx and http://download.microsoft.com/download/9/5/6/9560741A-EEFC-4... [PDF]

MSFT's STM strengthens my belief that STM cannot be done correctly without modifying the language semantics. Clojure avoids many of the pitfalls in the current user guide (2nd link I posted) by using semantics that are not possible for C# to adopt and remain backwards compatible; this will likely result in an inferior product. Standard MSFT.