Since SPDY is layered beneath HTTP it's relatively easy to roll out. At CloudFlare we plan to roll out SPDY when it is available as part of nginx because it will mean that can enable it for our customers with a simple on/off switch in the control panel (as we did for IPv6) without them making any backend changes.
The associated press release, with more detail: <a href="http://www.f5.com/news-press-events/press/2012/20120508b.html" rel="nofollow">http://www.f5.com/news-press-events/press/2012/20120508b.htm...</a>