I used Python + OpenCV during my MSc for face-detection: http://littlespikeyland.com/msc/project/ back in 2003/2004, so I ended up doing a lot of SWIG wrapping. A lot of the heavy lifting was done in C/C++, as I was running lots of simulations for a evolutionary algorithm.
I've used ctypes for a few projects now and wish I could have used it for that project. Might have meant I could have ditched a lot of the C/C++.