As many have already pointed out, Marco is a wonderful host. He gave us great suggestions for sightseeing, was very quick and responsive to our messages, and even helped us get a taxi early in the morning to the airport before the MRT was open.
Also, the area indeed is what you need for your first visit to Taipei. It's super hip, with lots of shops, cafes, and even historical buildings. We walked from Ximending to Lungshan temple, instead of taking the MRT, and we were able to see cool historical areas, including the Red House and Bopiliao historical block. There were also many street performers and great street art around Marco's place. It got a bit noisy on Friday and Saturday night, but overall we felt it was quiet.
The room is tiny. Especially if you're a tall man, you may feel claustrophobic because the ceiling is rather low.
The best part about the room is the bed: super comfortable with a hotel class mattress.
My biggest concern was cleanliness, which for me is extremely important, as I am allergic to dust. I have stayed in many Airbnbs and hostels but only here I felt the dust was unbearable. Opening the window helped a little bit but the window actually opens to a storage area, so you don't get much fresh air.
Don't count on AC, because the AC unit is an old model which makes excessive noise.
Also, the bathroom floor is kind of gross, with mold and stains. Bring your own flip flops to enter the bathroom and take a shower.