Jason Gunst has modified the Elementaty, Orta and Minty Freshness themes to integrate better with Unity in Ubuntu 11.04: the themes now have proper panel buttons and also the panel looks better (for instance, using the default Elementary theme, the Unity panel looks un-themed).
The modified Unity themes are available @ DeviantArt: Elementary, Orta, Minty Freshness ( <-- for manual installation, click the links) but because it's not that easy to use them, I've created a script for easy installation.
Warning: to be able to get proper buttons for the top Unity panel, the themes are called "Ambiance" so they will replace the original Ambiance theme. Also, you can't install all the 3 themes in the same time but only one. But don't worry, the script has an option to install the original Ambiance theme back if you want.
To install Elementary, Orta or Minty Freshness for Unity (Ubuntu 11.04), run the following commands in a terminal:
mkdir -p ~/Downloads/theme-unity cd ~/Downloads/theme-unity wget http://webupd8.googlecode.com/files/theme-unity_0.2.tar.gz tar -xvf theme-unity_0.2.tar.gz ./theme-unity
Then, you will be prompted to select a theme you want to install. Enter the number next to the theme, then open the Appearance preferences, switch to any other theme and then select the Ambiance theme. Yes, no matter which theme you've installed, select the Ambiance theme. As you can see, there's also an option to restore the original Ambiance theme
Update: the archive has been updated to version 0.2, fixing some errors (only display errors, they didn't cause anything to malfunction) that were displayed when running an application from a terminal.
Thanks to Jason Gunst for the tip and theme modifications!