I remember implementing an "<iron-ajax>" tag, and thinking that this is so wild and "Out There" that I may simply never understand.
Annoyingly, there is a whole "Hybrid" mode as well. So there is no distinction between V1 and V2. If you are confused,you go to the docs, they aren't giving you what you need, so you go to one of the sample elements, and it is written in V1. So you have to read the migration guide to translate what is actually happening....
Then Polymer Summit happens, and now it is all JS based which, is far better for me but now it seems pointless to stay on Polymer 2.0, and Polymer 3 is a preview with no docs...
So I aborted this path, went to Angular and to be honest, it is beautiful. It is almost trivial compared to the bag of questions and confusion I had going on with Polymer.
I do look forward to going back there though when 3.0 is available.