X Windows is a network oriented and client-server design with the X server responsible for all graphics operations.
MicroXwin is binary compatible to the Xlib API. However it is neither client server nor network oriented. Graphics operations are implemented in the linux kernel via a kernel module and makes this solution smaller and faster than traditional X Windows.
Why should you consider using MicroXwin.
Snappy GUI - MicroXwin has 2X times faster graphics, faster event handling, low latency and low round-trip delays.
Lower Memory Usage - MicroXwin's kernel based X server uses < 1/2MB versus 29MB used by Xorg's frame buffer X server.
Compatibility - MicroXwin is binary compatible with standard X11 at the Xlib layer. So you can run all the standard applications and window managers.
Now is available on Raspberry Pi. If you want to test a demo, download from the link below.
Download: microxwin.com > rasbianwheezy.tar.gz
More info: Compatibilidad