I don't think people that are running Nginx with spdy are doing so with the stable version. I started using spdy back when it was a patch you had to manually apply, before compiling Nginx.
(edit: clarified wording)
Anyway, doesn't spdy/2 have a huge security flaw in certificate management? I don't remember it well. If that's the case, it's good that they droped it.
Also the current mainline 1.5 version has implementation of spdy/3.