The latest Unity desktop version 3.8.16 was released on Jun 16, mainly fixes following bugs(see ):

#794556 Unable to load icon text-x-preview at size 48 in a loop
#795454 Display garbled upon restoring original resolution
#795458 Display garbled upon connecting external displays
#795459 Panel disappears after resolution change
#735031 Dragging the launcher with right mouse button is confusing as menu pops up
#750481 In a double monitor setup the Unity top panel in the second screen is cut at the right
#767642 unity is spamming ~/.xsession-errors when windows are closed
#767733 Dash button ignores transparency when clicked.
#750778 Menu key should open quicklist for the selected item in the launcher

To upgrade unity to 3.8.16 in Ubuntu 11.04 Natty, add ppa:ubuntu-desktop/ppa to software sources and then run update manager, or just run following commands:

sudo apt-add-repository ppa:ubuntu-desktop/ppa
sudo apt-get update
sudo apt-get dist-upgrade

Then, you can check unity version using:

unity --version

Unity 3.8.16 source code and changelog on