The ability to retrieve a list of client accounts and their details is useful when you're managing a large number of accounts using AdWords API. v201008 introduces ServicedAccountService, which brings similar functionality to new API. In v13, you could retrieve the list of client accounts linked to an MCC using getClientAccounts or getClientAccountInfos methods of AccountService. In v201008, you can use get method of ServicedAccountService to get same results. The following code shows the service in action.
ServicedAccountService also allows you to retrieve links that exist between the accounts. To retrieve the links, set the enablePaging field of ServicedAccountSelector to false.
In v13, you could retrieve the MCC alerts about your child accounts using getMccAlerts.