Some more upgrade notes

Author: Mark-H

en/04_Redactor/02_v3.x/Upgrades/From_2.x.md

@@ -2,12 +2,44 @@
 title: Upgrading from Redactor 2.x
 ---
 
-When upgrading from 2.x, expect a new and refreshed editor. 
+When upgrading from 2.x, expect a new and refreshed editor. Many features will be familiar, but some have also been removed or operate differently now. And of course, there's a lot of new features for you to use as well.
 
-Most of your configuration will be automatically converted to the new configuration sets, but some features have been dropped or work different now. 
+## First Upgrade
 
-It's worthwhile considering to start fresh, rather than trying to recreate an exact 2.x setup, to make the most of what's new. At the very least, take a good tour of the new configuration sets to see what Redactor 3 can do. 
+During the first upgrade to Redactor 3, your v2 system settings will automatically be converted into a [configuration set](../Configuration_Sets) named "Imported from Redactor 2". 
 
-[Start with the Quickstart](../Quickstart) to learn what Redactor 3 is all about.
+This imported set will be as close as a match to your old configuration as possible, but keep in mind not every old setting has a new option. 
 
-If you're missing features from 2.x, please let us know. 
+**Your imported set is not automatically enabled.** Navigate to Extras > Redactor Configuration to find it. Open it and make sure it was properly imported and works the way you expect it to. 
+
+When all looks good, you can enable it from either the configuration sets grid (right click it in the list) or [the system settings](../Usage/Content).
+
+**Important:** downgrading from 3 to 2 is **not supported**. If you're not sure yet if you want to start using Redactor 3 right away, start by upgrading on a development site and only upgrade production when you're happy. 
+
+Old system settings from v2, with a few exceptions, are removed on the first upgrade to v3.
+
+## Tip: start fresh
+
+While the automatic import is useful, we do recommend configuring Redactor 3 from scratch. Take a good tour of the new configuration sets to find out what Redactor 3 can do and use this as an opportunity to refresh your configuration.
+
+[The Redactor 3 Quickstart](../Quickstart) takes you through the highlights.
+
+## Dropped or changed features
+
+Please note this list may be incomplete
+
+- Allowed/denied tags and cleanup in general works differently now. See the Cleanup tab for details of what you can configure in v3.
+- The image float margin from v2 has changed. Previously you would set a margin for left and right floats separately, in v3 you set a single margin (in the Media tab) which will automatically be applied to the right side of the image.
+- Source code highlighting with Ace is no longer supported. Only Codemirror is now available (enabled by default).
+- The syntax for some plugins (like Clips) has changed. In most cases these will be automatically converted by the configurator. See the configurator for details.
+- Changing the available colors for the fontcolor plugin is no longer supported.
+
+The following custom plugins are no longer supported. Let us know if you think we should rebuild them for v3.
+
+- replacer (find & replace window)
+- speek (read content out loud)
+- contrast
+- zoom
+- imagepx
+- imageurl
+- breadcrumb