Guillermo's apartment is a wonderful choice to explore Brooklyn and NYC. I stayed for the entire month of August and even though it was stinking hot sometimes, the facilities allowed me to have a comfortable stay. The bathroom facilities are good, the kitchenette is great for basic meal prep, the bed is comfy and the courtyard is a great oasis to chill away from all the hustle and bustle.
One thing I would warn is that I encountered a couple of times a delay and lag in the internet. The bandwidth can be consumed through a couple of resources. Because the apartment is a dead zone, it can be a struggle to use netflix and research/ plan on the WiFi at the same time. Just one thing I would say to be aware of if you want to do a lot of planning there.
I recommend Guillermo's place and hope to visit one day soon!