Update README.md

README.md

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 # Polymer 2.0 (pre-release)
 
-This branch contains a preview of the Polymer 2.0 library.  The codebase is under active development, and APIs may change prior to the final 2.0 release.
+This branch contains a preview of the Polymer 2.0 library.  The codebase is under active development, features may not be fully implemented, and APIs may change prior to the final 2.0 release. 
+
+🚧 Note: Some tests currently fail on non-Chrome browsers; these will be addressed soon, but in the short term Chrome Canary is your best bet. 🚧
 
 ## Overarching goals for Polymer 2.0
 
@@ -88,8 +90,6 @@ Below are the general steps for defining a custom element using this new syntax:
 * Implement a static `template` getter to provide a template to stamp inside the element. By default the first `<template>` found in a `<dom-module>` with an `id` matching the element's `is` property is used.
 * `listeners` and `hostAttributes` have been removed from element metadata; they can be installed how and when needed but for convenience `ensureAttribute` is available. The ability to reference other elements in the listeners object has been removed (e.g. `'foo.tap': 'myHandler'`)
 
-
-
 Note that `Polymer.Element` provides a cleaner base class void of a lot of sugared utility API that present on elements defined with `Polymer()`, such as `fire`, `transform`, etc.  With web platform surface area becoming far more stable across browsers, we intend to hew towards sugaring less and embracing the raw platform API more.  So when using `Polymer.Element`, instead of using the legacy `this.fire('some-event')` API, simply use the equivalent platform API's such as `this.dispatchEvent(new CustomEvent('some-event'), {bubbles: true})`.  #usetheplatorm
 
 See below for a visual guide on migrating Polymer 1.0's declarative syntax to the ES6 class syntax in Polymer 2.0:
@@ -98,6 +98,10 @@ See below for a visual guide on migrating Polymer 1.0's declarative syntax to th
 ![image](img/migration.png)
 </a>
 
+## Polyfills
+
+Polymer 2.0 has been developed alongside and tested with a new suite of V1-spec compatible polyfills for Custom Elements and Shadow DOM.   Polymer 2.0 can currently be tested by loading the `v1-polymer-edits` branch of [`webcomponentsjs/webcomponents-lite.js`](https://github.com/webcomponents/webcomponentsjs/tree/v1-polymer-edits).  The polyfills are still under active development and are not fully ready for use in other browsers or for production.
+
 ## Breaking Changes
 Below is a list of intentional breaking changes made in Polymer 2.0, along with their rationale/justification and migration guidance.  If you find changes that broke existing code not documented here, please [file an issue](https://github.com/Polymer/polymer/issues/new) and we'll investigate to determine whether they are expected/intentional or not.