I agree that for some specific tasks OpenCV is not particularly useful (I have to write detector and trainer from scratch even there is opencv haartraining. The OpenCV crowd are most interested in applying it to real-time video processing and put little effort on Internet scale problem).
But for assembly optimization it is really not as useful as it used to be. Scalability is more about how to get sub-linear time complexity and efficient communication pattern. Nowadays c compiler can get fairly good assembly code and for low level optimization, human cannot compete with machine (how many people knows the particular cache line alignment trick on old core i7?). Multimedia instructions (SSE/MMX/3D Now) are useful but most of them can be done by function call instead of hand-crafted assembly.
He told me that they built it from scratch and did not use OpenCV. Some parts were even written in assembly.
Im pretty sure that this is the only web application that I use that has had major parts of it written in assembly.