Does anyone have any experience with any of these? I played around with the one on Code Project for a bit, but as soon as I tried to do anything complicated I got some nasty uncatchable exceptions (i.e. Msgbox exceptions). Cross platform (supports Mono) would be best.
I started out with opencvdotnet but it's not really actively developed any more. Further, support for the feature I needed (facedetection) was patchy. I'm using EmguCV now: It wraps a much greater part of the API and the guy behind it is very responsive to suggestions and requests. The code is a joy to look at and is known to work on Mono.
I've wrote up a quick getting-started guide on my blog.
We use OpenCVSharp the google code website is in Japanese but it uses the latest OpenCV builds and impliments IDisposable throughout. It seems to provide more functioanlity than any of the others we have seen to date and is still active. It has quite extensive example programs as well.