Starting with version 11.04 alpha 2 (to be released on February 3rd), Xubuntu will use a new theme called "Greybird" as the default theme. The GTK theme is inspired by Elementary but there are quite a few differences between Greybird and Elementary.
Work in progress
Currently the window borders look the same as in Elementary but this will change in the upcoming iterations. Further more, there are many elements that still need tweaking and further improvements such as the notebook-style (the tabs), selected background color, expanders and more. Also, the background color may change to a darker grey.
The reason the Xubuntu developers decided to go with Greybird for 11.04:
We took a conscious step from the polarizing and intense blue to something that proves easy on the eyes for everyday work (and also because one focus of the natty-release is accessibility). That's why "greybird" is not as vibrant as Elementary.
Those who are concerned about the performance when using this theme shouldn't worry as the theme uses only an engine - Murrine.
Check out the previous default Xubuntu theme - Bluebird.
You can download Greybird from HERE.
What do you think? The Xubuntu developers are always open for change so let them know what you like and what you don't in the comments below. You can also contact them @ #shimmer or #xubuntu-devel on irc.freenode.
Thanks to Simon Steinbeiß for the info and tip!