GrAnd:
I checked behavior of my A620 again and you are right - miscellaneous values (in my case aperture, ISO, subject distance) are shown on LCD whether this option is on or off, but values are not updated during video recording if this option if off (altough camera is varying aperture and iso during video recording, dependion on lighting)
But, on S3IS, these values are not shown during video recording, except on half press of the shutter. It would be fine to have this values shown also during video mode, mostly to check if the focus distance is right
a710is:
Yes, S series is different (I bought second hand S3 several days ago) than A series. You can set autofocus mode to continuous, an camera will be refocusing during video recording, or you can force manual refocus with half press of the shutter during video recording. If you fully press shutter, jpeg is saved and video recording continues further (well - if raw is enabled through CHDK, video recording is also terminated, which was discussed in other thread)