I had a great experience staying for a month with 2 kids. Sebastian arranged an early check in for us, so we did not have to wait.
The appartment is extremely well located, a 2 blocks away from the gorgeous Retiro park. A LOT of restaurants nearby, so you never actually have to cook if you don't want to. Subte is < 5 minutes away and you can get anywhere in the city. Puerto Madero is a 15 minute walk away. We really liked the view of the basilica and old cordoba hotel out of the bedroom window.
The appartment was clean and fresh, modern equipment, clean sheets, etc. It also had everything we needed for cooking, enough towels for a family of 4 and eating at home and a good washing machine .
The hosts are very responsive. We accidentally locked our keys inside the appartement on day 2 or 3 of our trip, they arranged the building staff to help us unlock the door in under 15 minute. Definitely recommend!