I know it has become someone popular in the xenforo community since digitalpoint and theadminzone both use it. The images are the only thing I can think of that keeps vbulletin users from using SPDY. MaxCDN and CloudFlare both support it as well.
I am not sure how many people still ready this forum but I would install this in a heart beat.
Here is a good read as well where thethemefoundry switched to SPDY.
https://thethemefoundry.com/blog/why...-cdn-spdy-ssl/