I believe that's new for this year. 2011 was a total mess as the registration page was just a ColdFusion site run by their event management vendor, and they were clearly used to medical conferences and the like that don't get the same swift response that I/O would get. The registration site served up way more 503 errors than pages.

Last year was better because Google took it in-house, but it was still an F5-fest.