PERFECT!
All on this stay was perfect, by far THE BEST experience with AirBNB so far.
- Martha was very kind and accessible, having waited until 11pm to let us in (our flight was delayed)
- The apartment is very cozy, modern, full of space and natural light. It had all supplies that were needed (full equipped kitchen, bed linen, towels, etc). We really felt at home.
- The location couldn't be better - full of restaurants, bars, shops, supermarkets, ATM, bus, metro - all within few blocks
- Martha also recommended Gustavo, a nice taxi driver to pickup / drop at airport

In summary, I would definitively stay there in my next trip to Buenos Aires.