Requesting "Ultra-smart" TM-based backup feature

[dnanian]

Actually, no: the work here is done by fsevents, not Time Machine, really. And improvements to scanning can be made in future versions of SD, but the more coupling we have to complex software systems (Time Machine, fsevents), the more likelihood there is that a flaw in those systems will impact all your backups, rather than just one.

In general, that's unwise. SD! tries to do things in a simple, straightforward way. It's easier to test, more reliable, and the only real downside is a bit of extra time taken. Given that, on my 3-year+ old system, it takes < 18 minutes (16 minutes last time) to update a backup of over 2.5M files to a regular FW400 drive, the time savings isn't worth the additional risk/coupling until those systems are very well established (and perhaps not even then).