Next GIMX releases will use a new event library called GE for “GIMX Events”. In Linux, it directly interfaces with evdev instead of X through a modified SDL 1.2.14. The event path is shorter: it previously was evdev->X->SDL->GIMX, it is now evdev->GIMX. Reading events from evdev also allows to process events in an interrupt-driven manner. It means that it is possible to process input events as soon as they are available.
Getting rid of the X dependency allows to run GIMX (emuclient) without desktop environment, which better scales to small or old Linux targets. An example of small Linux target is the Raspberry Pi.
GE still uses the same modified SDL 1.2.14 in Windows. There should be no performance impact on this platform.
There is a specific page on the wiki that shows how to use GE.