Yes I had read that - but it provides no details about what a sendfrom actually does (about the same as using "bitcoind help sendfrom").
This is aimed mostly at shared wallets that are used by webapps and that maintain a balance right inside the client for every user (or non-user account).
The accounts are not permitted to go into negative, only the default account "" may have a negative balance.
Getting to pick which address actually sends the coin isn't available without patching the client.