Here's a blog post containing some of my thoughts:
Can someone comment on whether push notification of cached-item changes is something that will be supported in future bits/releases?
As Ankur mentions, support for notifications is very high on our priority list. Please see a follow-up post at http://blogs.msdn.com/velocity/archive/2008/06/03/microsoft-project-code-named-velocity-followup.aspx.
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