This was a super find! The apartment was nice and David and Carole were very accommodating. They even agreed to let us check in late... and our flight didn't get in until after midnight. It's a sweet little place that is well kept and clean. The bed in the master bedroom was comfortable--soft but not saggy. (Do note for size determination it's a double bed: not quite as big as a queen, I do believe.) Given that hotel rooms seem to be notoriously small in HK, it was super to have an entire apartment at such a reasonable rate.
They gave the two of us a single key, so if you want more, I'd advise to give them a head's up so they can prepare. They were quite willing to get me a second key, but if I'd told them ahead of time it would've been easier.
The apartment's situated very close to the Mong kok metro station. There are buses on the street out front and taxis are easy to hail right out the door as well. The entrance to the building is adjacent to a DBS atm.
Mong Kok is bustling and food is plentiful within walking distance--as well as having a supermarket right across the street.
Thanks again to David and Carole!