This is really just a ‘re post’ of an excellent blog article demonstrating the features of repadmin. I learned quite a bit from reading this and hopefully this will benefit other AD Administrators out there.
I like the summary command: Repadmin /replsummary *
And /syncall with the /A(ll partitions) P(ush) e(nterprise, cross sites) d(istinguished names)
For example, you can see which changes have not yet replicated from a server, as well as what changes have replicated since the last time the command was run, with /showchanges:
repadmin /showchanges destination_DC source_DSA_GUID domain_DN