The website mentions that you are using google-diff-match-patch in the JavaScript client to merge changes, it seems as the API does not require the developer to actually specify things like "the user added an A at this position" as opposed to just "commit the changes to this entire object". Is there a reason other than simplicity for this API (I guess maybe because CoreData doesn't have that abstraction, and I presume your timeline was to start with figuring out how to sync CoreData), and on iOS are you also using google-diff-match-patch (there was not the same explicit mention of it in the documentation there)? (edit: Actually, I guess the comment from zbowling about DiffMatchPatch answers the second half of that. ;P)

BTW, this is generally really awesome: I am (right now, as in I'm sitting there right now ;P) helping teach a class on cloud computing at UCSB that happens to currently be discussing database synchronization and replication; after spending a bunch of time today discussing "how PostgreSQL is implemented and the basis of different isolation levels in the SQL standard and in MVCC" I took the time to tell everyone about Simperium (which probably makes more sense if I mention that I've looked into building something similar before for my projects; I'm glad someone else finally seems to be coming at it from the correct mindset). Everyone here seems to agree: this is going in a great direction.