I just tested a CG102 and it was essentially seamless in changing files. A ticking clock skipped nothing perceptible (certainly less than 1/4 second) when files were changed.
On a different camera (DOD HD200) I did find that some Class 6 cards did not work as well as others. In that case the second file would start, but then quickly stop with a very small file (38M or so). Selecting my fastest SDHC cards got around the problem.