Having suffered from some AD replication issues in the past (the dreaded lingering objects), its been at the back of my mind on how to keep an eye on replication between all the DC's.
Also a frequent question from the helpdesk goes along the lines of they've made a change to somebody's AD account and how long is it going to be before that change will make it around to all of the DC's? In the past I've kind of stuck my finger in the air and given an approximate time based on replication intervals in the site links.
So how about some Powershell which checks AD replication latency for you (and at the same time confirms all DC's are replicating) so you can give a more precise figure on how long it takes for a change to replicate the whole way around?
Brandon at the BSonPosh blog has a frankly brilliant post with a script you can run which creates a temporary contact in AD, then polls each DC until it appears, records the time taken and finally removes the test contact.
For me this was a Snover moment (i.e. the top of my head exploded!), this is so useful for me its unreal, and possibly the best bit: my finger in the air estimate was pretty darn close. :-)