A very good decision, Polymer is a breeze to work with. It also shows that google is very confident in it.

Polymer has been a very opinionated framework. It really seems in the last ~6 months that they're really moving back to their web component roots and being less of a rigid framework and more of a library with 'best practices'.

They're still a bit under-cooked on their data-binding stuff in my opinion - I've found it a bit unstable and hard to use (there could be some causation going on there).

Opinionated? I've been mixing it with jquery and other libraries just fine. Its really relatively small piece of code (if you rule out the polyfills).

I wouldn't call it a framework any more than I'd call React a framework.

Other than web components not being fully supported yet by browsers is there any other downside to this compared to react+redux/vuejs or angular? I'm just asking as I haven't tried polymer until now but I'm pretty familiar with the mentioned fw's.

For the browsers that don't fully support components yet, Polymer should take care of it for you.

No downsides, I've been sucessfully using polymer on unsupported IE10 and in our use cases we haven't encountered a blocking issue.

I guess it doesn't say much for their confidence in angular 2 that they don't actually use it for anything.

I think web components are a step sideways (and forwards) from libraries like Angular. Not necessarily that they don't have confidence in them, but more that they're taking a punt with what they perceive to be the next evolution.