That's good to hear. Generally, we should be fine as most apps don't write files. Some do make reads/writes to HKLM, which I assume will need UAC elevation.
Possibly not, depending upon how important it is that it's in HKLM. Given that VB6 won't manifest executables as Vista+ compatible, they'll get File and Registry Virtualisation applied to them and thus writes to HKLM will be "faked" into HKCU so that only that app will see the change.