Core Image seems to be horribly broken with 10.11.
Standard blur gives a frame rate of around 7fps with a 640x480 input video feed.
Samplers don't seem to work inside custom kernels correctly.
Editing filter function doesn't seem to work correctly.
Basically... I am very surprised that this was released considering that I have spoken with around a dozen people who have had similar results on a wide cross section of hardware spanning the past few years. Also, Core Image wasn't doing that well last OS version, so I thought someone might have addressed it, instead of adding even more bugs.
Not to be patronizing, but it is possible to add branch logic, etc., without totally hosing existing kernels.
The language should have just been left the same, deprecated, and replaced by some GLSL based standard. The proprietary systems with poor performance, and lots of hype, that never really deliver, wind up being a really big time and money drain.