Here to report getting the spinning wheel like crazy for the output section of templates, for all types (page, content blocks, product stuff). The only one that seems to be working/accessible is the default page template.
Here’s a long, boring look at it happening: http://recordit.co/Hu4lqezBAj
Everything else is loading at normal speeds so I don’t think that it’s just things taking long to load in general. I’ve tried logging out and back in again, it doesn’t seem help. As an example for the wait time, I’ve had the Default Product List (3up) template trying to load the entire time I’ve written this forum post with no output showing up yet.
ETA : it appears this is only happening for me in Chrome. It also happened earlier today on a different machine.