We really enjoyed our 2 weeks in Sebastian's loft. While it is a bit far from any central areas (Palermo Hollywood is a 15 minute walk away), it is really close to a bunch of bus stops.
If you'll just be sleeping in the loft, and going out all day and returning at the end, it's brilliant. There's multiple bus stops within a stones through of the loft which will take you to Centro, La Boca, Belgrano, Retiro, pretty much anywhere you want to go. It's super easy.
The loft is on a very noisy street, so the sound of traffic is loud and constant. If you're a light sleeper, this may not be the best place for you. That said, most places we stayed in in BA were very noisy... it's a noisy city. Bring your ear plugs!
We were there in the middle of summer, when the temperature was mid thirties every day... the airconditioning kept us cool, but we did have to crank it all afternoon for it to cool down enough upstairs to sleep there. Lo siento madre tierra!
Sebastian was really responsive and helpful throughout our stay. For example, when the internet broke, he had a technician at the place fixing it within 24 hours - genius. I don't think i could pull that off in Australia.
Overally we really loved staying in the loft. The facilities are all excellent, there's great wifi and cable TV (Which we never turned on) with Netflix, a cool little desk to work at, and a nice sitting area near the kitchen for eating meals.