How good are todays search engines (Google/Bing etc.) to index SPA?

at work we are using EmberJS for an internal application which is nice. But for external applications, how viable are SPA frameworks if you have to rely on good SEO?

Can todays search engines really manage to index pages generated by javascript, like done by frameworks such as Angular and/or Ember? If yes, how good are they? I know that there are some projects that redirect bots to a prerendered page with phantomjs, but it seems like more work than it's worth.

Would be nice to know for future projects in the near future but also since I'm curious.