I've managed to install elementary desktop by rebuilding ubuntu-extras-keyring locally on my system, like this:
mkdir somedir; cd somedir
sudo apt-get install -y debhelper
wget http://archive.ubuntu.com/ubuntu/pool/main/u/ubuntu-extras-keyring/ubuntu-extras-keyring_2010.09.27.{tar.gz,dsc}
tar -xf *.tar.gz
cd ubuntu-extras-keyring-2010.09.17
debuild -i -us -uc -b
sudo dpkg -i ../ubuntu-extras-keyring_2010.09.27_all.deb
After that, elementary-desktop will install, but will error out at the end because it depends on systemd-shim which is no longer needed nor wanted with 15.04 having a full SystemD implementation.
When it errors out, run
sudo dpkg --force-depends -r indicator-datetime
sudo apt-get purge unity-control-center unity-control-center-signon
and it should complete the installation.
I expect in the near future the Elementary folks will fix their repository to handle SystemD properly - Ubuntu 15.04 move to SystemD was done a few weeks before the official release and the Elementary guys probably didn't have time to adapt to that.
After installation, you can log out and see "Pantheon" in your display manager's session list, but if you try to log in you'd get just the blueprint paper styled Elementary "beta wallpaper". The problem is that the session starts Slingshot and Gala, but not WingPanel or Plank. Currently I'm using using Slingshot's ALT-F2 shortcut to open the launcher and run Plank and WingPanel manually (just type the name in all lowercase and hit ENTER).
The typical route to starting X from the command line (TTY) is to use .xinitrc and/or startx.
First, find out which command starts the Pantheon session. Look in /usr/share/xsessions for a .desktop file named after Pantheon, and check the Exec line in that file:
$ grep Exec -R /usr/share/xsessions/pantheon.desktop
Exec=gnome-session --session=pantheon
For a one-time run, you can do:
startx /usr/bin/gnome-session --session=pantheon
For a long-term setting, use .xinitrc. Usually, you wouldn't have an .xinitrc present. So, create one containing:
#! /bin/sh
exec /usr/bin/gnome-session --session=pantheon
Then run startx.
Check the Arch Wiki article on .xinitrc to see how to make more a full-fledged one.
Best Answer
on desktop you can't put launcher. elementary does't support "have file manager handle desktop" in dock (plank), open the app and his launcher is been show in dock. right click on icon and in meny go to "keep to dock". in wingpanel, same as unity panel, is possibe via dconf-editor some, but launcher to panel not. indicators in panel & message meny work like in unity panel