This place was great! I was very comfortable and I felt like the host really went out of his way to make it a nice space. Utnisnin fact very close to the MRT station, and the apartment and building are very nice by Taipei standards.
In case anyone cares, you CAN flush toilet paper in the apartment, which is not the case everywhere in Taipei.
I felt like there was plenty of space for just me. My girlfriend joined me for the last few days and a couple staying here for a while would probably be fine. I think 3 people would probably start to feel crowded after more than a few days.
There is a gym in the building, but most of the machines are old and many are broken, so I wouldn't really count ok being able to work out there. There is another, nice-looking gym right accriss the street though if you really need to work out.