Release highlights since 337.19:

Fixed a bug that caused X to crash when querying clock offsets for non-existent performance levels.
Added support for the following GPUs:
GeForce GTX TITAN Z
GeForce GT 740

Fixed a performance regression when running KDE with desktop effects using the OpenGL compositing backend.
Fixed a bug that caused duplicate entries to appear in some dropdown menus in the "Application Profiles" page of nvidia-settings.
Fixed a regression that could cause OpenGL rendering corruption on X screens with 30 bit per pixel color.
Fixed a bug that caused nvidia-installer to crash in environments where /proc is not mounted.
Fixed a bug that prevented module signing from working correctly for the NVIDIA Unified Memory kernel module when using module signing keys generated by nvidia-installer.
Added support for X.org xserver ABI 18 (xorg-server 1.16).