Hi, amathie. Welcome.
It's important to recognize that a Safety Clone is
not a backup, so don't think of it that way. (See
my blog for more on this naming issue.) But a full clone -- "Backup - all files" -- is useful in case of failures.
The Safety Clone is very useful for System Isolation when testing out OS updates and the like, however, since you can roll back quite easily by just rebooting back to the original.
But, highly copy protected programs are a huge issue. Obviously, we can't copy their 'authorizations' or they wouldn't be very protected. On a Safety Clone, the application stays on the original drive, and this tends to keep the activations working (though I obviously haven't tried everything out there, so this might not always be the case), but to be certain you'd have to try it...
SD! is compatible with Tiger, given the caveats listed in the FAQ. Tiger's obviously brand new, and has its own issues, but we've done our best to document each of the potential problems along with workarounds.
Hope that's useful.