Macs have shipped with the X Window System, or X11, ever since the release of OS X 10.3 (Panther) in 2003. For those of you who are unfamiliar with X11, it is a means of providing a graphical user interface for certain applications, mostly Linux based. The implementation of X11 in OS X allows the user to run apps ported from Linux, or that rely heavily on the X Window System, with ease and stability.
OS X Mountain Lion will have support for the more frequently updated open source XQuartz rather than X11, and I really like the sound of that. I’ve always been a fan of open source software simply because of the large support communities and frequent updates. Like I’ve said before, I was an avid Linux user before making the switch over to OS X, so a lot of the applications I’m familiar with are based on X11.

Image courtesy of http://osx.iusethis.com/
For example, I use the GNU Image Manipulation Program, or GIMP for any and all graphical work; even the header of this blog. Upon switching to OS X, I wasn’t about to pay a fortune for Photoshop when the GIMP was already just as powerful, and free. So, I grabbed the Mac version of GIMP and ran it under X11. The only thing was, on Lion, the official X11 was packed full of annoying bugs, and at one point X11 wouldn’t even run at all. That’s when I made the switch to XQuartz, and I haven’t looked back since.
For the average end user there are no noticeable aesthetic differences between the two, but it seems like the official X11 is no longer getting along with current versions of OS X, where XQuartz is running damn near flawlessly.
For more information on XQuartz, visit: http://xquartz.macosforge.org/