I haven't used it myself. Read on a couple of local webmaster's forums that they use it to cash out paypal. (Transfer to xoom account, then withdraw at Banco Frances).

Frankly, I don't know whether it is practical. For small amounts there are ATMs, for bigger amounts Moneygram seems to be cheaper (and more trustworthy since it is American Express division).
I've used it to send money to Nicaragua several times. It has worked flawlesly and it
is far cheaper than Western Union!