The client side code works pretty well. Of course, we could make local data store origination more universal, add input data validation based on the current grid structure, etc. But it can be left as it is so far.

The server code is terribly simple. Choosing a single-piece CSV as the type of data transfer and saving may result in the ultimate simplification of operations, but the price for that is loss of flexibility. In theory it is possible to replace the current saving scheme with something more elegant, allowing to use simultaneous access to data and smarter synchronization (since Gears was meant to be used in such scripts). But this will result in loss of code simplicity. So, maybe next time.

The usage of local data store significantly improved usability with a relatively small amount of code needed. Taking into account the fact that most browsers are advertised as powered with local data stores, such a solution might be implemented without any outside plugin in the offing.