We stayed at Alejandro's place during the week of New Year's and enjoyed our stay in Palermo. The location is great, and convenient to the neighborhood's great restaurants and shopping. There are many nearby grocery markets to buy water, snacks or other necessities. The metro is also close by to go towards the city center.
The building has nice facilities that we took advantage of, such as the gym, sauna, pool and laundry (you can buy tokens at a nearby kiosco). There is a security guard at the building entrance, so you feel safe. The neighborhood is fairly safe in general, and has improved since I visited in 2010.

We were comfortable in our stay, and felt at home. The bed was comfortable, AC worked well (an Individual unit in both rooms), wifi worked well with no issues, shower had strong, hot water, and we enjoyed the balcony for both relaxing in the evening and for drying clothes. The closets were spacious for unpacking and hanging shirts.
The refrigerator was making a somewhat loud clanking noise on occasion, which could be adjusted if you turned the temperature down, but we had items in the fridge.
The building and apartment has a cleaning service that came 2 or 3 times during the week we stayed. Usually they came in the afternoon, which was good while we were out for the day. The cleaner they used on the floor was quite slick, to the point I couldn't walk around in socks.
Alejandro was very attentive as a host, and very quick to answer questions on whatsapp (in English or Spanish). He graciously had offered two bottles of wine as a welcome to the apartment. His assistant Diego was thorough during the checkin process as well.
It should be noted there is construction of a new building next door. Unfortunately at the time, they were working at the level of our floor, so the noise was pretty loud to the point you couldn't sleep in. This is out of control of Alejandro, and won't be an issue for long, but it affected our stay.
Overall, we enjoyed our stay in Palermo, and look forward to coming back. We would definitely stay in Alejandro's place again.