Human Murine And CLearlooks Theme were removed from Hardy Beta in latest update.
The new themes were considered a improvement over the old human engine based theme but in my point of view it is difficult to compare because the difference between them is more then just color palette they use different engine .
Human theme in my point of view was a good compromise but now we have better alternative.Even if these theme can not be made default due to some political or technical reason ( still waiting for the question to be answered ) .It can still be made optional it is far better then the other theme included which are the reminiscent of the old days of gnome without cario.
Currently Ubuntu uses the "Ubuntulooks" GTK engine to draw widgets, which was forked from Clearlooks some time ago, but this engine appears to be no longer maintained
For more detail about the theme go to
http://tombuntu.com/index.php/2008/03/02/two-new-themes-arrive-in-ubuntu-804/
It provides nice overview of the new themes in hardy but murrine image is outdated it does not use striped menu bar and has same clean interface as clearlooks based theme.
For changes in the clearlooks based engine go to
http://arstechnica.com/reviews/os/gnome-2-22-review.ars/3
it gives a nice summary of the changes in clearlooks engine which will help u to know small subtle improvements which are also present in human clearlooks theme
Ubuntu question relating to this
https://answers.launchpad.net/ubuntu/+source/human-theme/+question/28643
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