The OnePlus X shipped with Android Lollipop, and this update doesn't change that. But you do get the manual camera mode that hit the OnePlus 2 in September. The changlog also includes the option to save photos to a microSD card. Plus dual SIM preferences have returned to system settings.
Aside from that, this is largely a bugfix update. Though sometimes seeing a bug get squashed is more exciting than new features.
Manual mode for Camera App
Save to SD card option in Camera App
USSD bug fix for India
Added dual SIM preferences back in system settings