Prior to our trip I was concerned about safety and being mugged given the various posts on safety in Buenos Aires. Now that we are back I thought I should post a brief trip report which may help alleviate some concerns.
My wife and I walked extensively during our 3 day trip and did not encounter any issues nor did we feel at risk. We did look like tourists and carried a camera but took sensible precautions of reading maps in cafes rather than street corners and walked with a reasonable purpose and did not wear obvious valuables (albeit my Omega watch was visible).
We did a day of mostly walking which involved taxi to La Boca, then local bus to San Telmo (on this bus we saw a local woman get out of her seat to assist an elderly tourist couple who were struggling with the payment system - and no she did not pick pocket them!). From San Telmo we walked to Monserrat, San Nicolas and onto Recoleta. We did have a female guide for part of this walk (La Boca to Monserrat) which helps with knowing where to go but I did not feel threatened even when walking in a quiet street where there was only us and a group of male youths. This was a great walk and we felt we experienced a good part of the city's history, culture and architecture from it.
On other days we used the Subte and walked through Recoleta and extensive parts of Palermo and again did not feel threatened. Buenos Aires felt no different to any large city where you have to be careful, plan in advance where you want to go and not look like a victim. I don't know if it makes a difference but most of our walking took place at the weekend. I hope this helps others concerned by various posts but you still need to be vigilant.