I used gphoto2 to find out how many clicks. But I am a computer programmer, and love working with Linux.
It did not come with the latest firmware. I will be updating that tonight.
I read a thread here somewhere that the site EOSCount.com no longer works on 5D3s that have been updated to the latest FW. I would be very interested in your experience with gPhoto2 after you update your FW. Could you please post back with your results?
Thank you, Tim!