I've never used it myself, but it is often suggested/recommended in these forms.
I had two computers synced for a long time, then one of them went down and was fixed after two months.
Now we've been using it for a while, but I haven't had time to sync them up. Now we have two similar computers and I want to essentially merge the files we have on both of them.
What I need is to be able to transfer two similar files using certain rules.
Specifically: Replace older files with newer ones
I've found stuff that transfers files, find dups, etc... but nothing that will allow me to make a simple rule.