I recently got OpenCV up and running on my Zynq-7000 based Zedboard. The performance of the OpenCV samples I ran was very good even without using the FPGA fabric. I didn't get my OpenCv from Xilinx, but rather downloaded and built it from the generic ARM Linux source.
I really wanted to see how compatible the Zynq is to the rest of the ARM CPU/SOC world. The Linux distribution I'm using (Xillinux) is made for the Zynq, but pretty much everything else I used was generic. I built CMAKE, Mjpg-Streamer and OpenCV from non-targeted source files. The Mjpg-Streamer source I used was made for the Raspberry Pi. The others were generic ARM Ubuntu sources. I also downloaded and used a large number of generic source libraries - all of that without touching a single line of code.