[smarx]

I suppose your scenario for (iii) is reasonable in the case of sharing a datastore among multiple users. In that case, you'd probably still want all of that user's devices to use the same conflict resolution strategy.

BTW, (for now) the Datastore API doesn't support sharing among multiple users.

Given the relationship the Datastore API has between the client and the server, it's also possible for a client to use a custom resolution rule (though this isn't yet exposed in any of our clients), which would let you do smarter things like look at the changes that were made and decide based on app-specific logic which one should win. I personally think that's a big advantage, but as I said, it's not one that's yet been fully realized.