> Also, I always have this vague fear that I'll rsync in the wrong direction

It's the same direction as cp/scp ... You could easily do it wrong, but you must be afraid to do anything other than maybe cat < source > dest because that's clear?

> or accidentally blow away unrelated files in rsync's efforts to fully synchronize two directories (can't remember if this is a valid concern).

I think you need --delete for this. As I recall, it's sometimes more tricky to get it to delete the files you wanted it to delete and you're more likely to end up with extra files than removing files you didn't intend to.