Due to all the turmoil and financial controls the US dollar has shot up in the past few weeks. Today it's up to about 5.80.
Tourists can utilize services like www.xoom.com to get up to 5.43 pesos to $1 US which is MUCH higher than the official rates.
I've spoken to several people that successfully used it so this might be an option for those of you staying in Buenos Aires and need larger amounts of pesos.
Notice the part on this link for "Dolar informal".Edited: 23 May 2012, 03:04