WF 4.0 new features (PDC08)

MSDN Channel 9 link

- Activities have in/out Arguments that can be bound to scoped Variables

- persistence points, no-persist zones

- adapting to mid-stream process changes. activities can be updated midstream

- tracking service - 28'

- WF4 vs WF3 - 33'

- Support for Partial Trust Env

- Rehosting improvements (nothing in particular demo'd)