I know MS said that before about the seemless migration from FP 2.x to VFP but this upgrade you are looking it is really seemless, no code should change, I did that with 3 major Apps with no problem. You can even open previously migrated files to VFP 7.0 in VFP 6.0 with the exception of menu files.

As for the client ability to run both VFP 6 & 7 apps, that should not be a problem either provided you leave VFP 6 dlls whereever they were installed.

In short, it is an upgrade worth going through.