qubes-release: fill release-notes (based on the one on website)

qubes-release/README.Qubes-Release-Notes

@@ -1,6 +1,43 @@
-README.Qubes-Release-Notes
-==========================
+Qubes R3.0 release notes
+========================
 
-This is a placeholder. There are no useful release notes in here.
+Major new features since 2.0
+----------------------
 
-Sorry about that.
+* Xen 4.4
+* Qrexec 3
+* Debian templates
+* Whonix templates
+* Build system improvements
+
+For other features take a look at [completed tickets](https://github.com/QubesOS/qubes-issues/issues?q=is%3Aclosed+is%3A:issue+milestone%3A%22Release+3.0%22+label%3Aenhancement)
+
+Known issues
+------------
+
+* For known issues take a look at [our tickets](https://github.com/QubesOS/qubes-issues/issues?q=is%3Aopen+is%3Aissue+milestone%3A%22Release+3.0%22+label%3Abug)
+
+It is advised to install updates just after system installation to apply bug fixes for (some of) the above problems.
+
+Downloads
+---------
+
+See [Qubes Downloads](https://qubes-os.org/doc/QubesDownloads/).
+
+Installation instructions
+-------------------------
+
+See [Installation Guide](https://qubes-os.org/doc/InstallationGuide/).
+
+Upgrading
+---------
+
+### From from R3.0rc1
+
+If you are using Qubes R3.0rc1, just install system updates, there is no special steps required.
+
+### From R2.0 or earlier
+
+The easiest and safest way to upgrade to Qubes R3.0 is to install it from scratch and use [qubes backup and restore tools](/doc/BackupRestore/) for migrating of all of the user VMs.
+
+Users of Qubes R2 can upgrade using [experimental procedure](/doc/UpgradeToR3.0/).