So, I used PFDAVAdmin yesterday to make some changes to the replicas of some huge public folder trees. I used the Custom Bulk Operation to perform a Replica List Operation type and selected the Merge action. It asked me for the list of stores I wanted to add to the replica list and then it asked me for a list of stores i would like to remove from the replica list.
Doesn't really tell you that this does both functions independently and is not a Search & Replace feature.
For instance, say you have a folder tree like the one listed below. The \RootFolder has a replica only on ServerA but \SubFolder3 has additional replicas on ServerB. You want to move those replicas from ServerB to ServerC.
\RootFolder
\SubFolder1
\SubFolder2
\SubFolder3
\SubSub1
\SubSub2
If you use the Merge action against \RootFolder to add ServerC and remove ServerB, the tool will add ServerC to the replicas of the \RootFolder and all subfolders and you'll end up replicating the ENTIRE \RootFolder structure to ServerC, not just the folders where the ServerB replicas were removed.
This could be very un-fun if the \RootFolder is very large. You'll probably get a call from one of your WAN guys asking why you're hogging all the bandwidth. :)
Instead, in SP2 for Exchange2003, they've added a context-menup for moving replicas. More info on that can be found here.
You've been forewarned.