I stayed at Gustavo's place for about a month while I visited Buenos Aires and took an intensive Spanish course.
LOCATION - extremely convenient and safe. The apartment is in the Microcentro and is very quiet. This is a business and shopping mall district and is a reasonable walk to the obelisk and the theatre area. There are little markets all over the place, so anything you need at the last minute is readily at hand. Be aware that the Microcentro is one of the more expensive areas in town.
SAFETY - I especially liked the presence of the doorman, as well as the need for guests to buzz in and buzz out as well.
LIVING SPACE - The apartment has all of the amenities described and has a gorgeous view from the bedroom.
FACILITIES - the bathroom has good water pressure and plenty of hot water. The kitchen is small, but reasonably equipped. I had just a couple of intermittent problems with the internet, but otherwise the connection worked just fine. There's also a good TV channel selection through the TV service.
All in all, highly recommended!