Twitter: creatify_me
Github: creatifyme
JavaScript apps are rendered client side or browser. With universal rendering you can serve up a fully rendered page.
Most search engines without universal rendering
Google search bot without universal rendering
All search bots with universal rendering
Google search bots without universal rendering
Google search bots with universal rendering
It's more work for your server, so your HTTP response will take a little longer to return. A lot longer if your servers are under heavy load.
Universal rendering increases the complexity of an app
renderToString function is slow and just kind of lame