Having App Store accounts in more than one country is almost a necessity for us Brazilians, who are deprived of the games area in the national store. An American account allows us to download games available for free, while the Argentine version accepts our Brazilian credit cards.
The problem is when it comes to getting organized: application updates only appear when you are signed in to the account from which it was downloaded. This is unpleasant, because if you rarely connect to a particular account, you never know when updates are available.
For our experiences, firmware 3.0 seems to solve this problem.
It is already known that the future firmware will allow the exchange of accounts directly on the device (read «Firmware 3.0 may allow the management of several App Store accounts directly on the iPhone»), but until then no one had commented on how the management of updates would be. As far as we can tell, all installed applications will receive notification of update, regardless of which account they belong to.
But it seems that the service is not yet fully implemented. When trying to update an application from a different account than the one present on the device, the system gives an error, warning that the store is different.
Another probable facility to be implemented in the future iPhone OS 3.0, with a promised launch for the middle of this year.