I store some data in my iOS app directly in a local .sqlite file. I chose to do this instead of CoreData because the data will need to be compatible with non-Apple platforms.>
I've considered the possibility of transferring a database file through iCloud but I think that I would run into classic problems of timing - slow start for the user - and corrupted databases if the app is run on multiple devices simultaneously. (iPad/iPhone for example).
Sooo. I've had to use the transaction logs method. It really is difficult to implement, but once in place, seems ok.
I am using Apple's SharedCoreData sample as the base for this work. This link requires an Apple Developer Account.
I did find a much much better solution from Tim Roadley however this only works for IOS and I needed both IOS and MacOS.
rant> iCloud development really has to get easier and more stable! /rant