When I Save() in the wp7 emulator it seems really slow. I've even tried saving by creating a new thread but it still lags the interface.
Was wondering if you've experianced this. I've tested it on two machines and I'm worried that this might also happen on live.
It seems to me (looking through the debugger) the main lag is when it saves out each table in turn. I notice a lag on GetUsersStoreForApplication which is called per table access perhaps you could share this between the table writes?
Forgive the spelling :)