This is perfect for a short break in Hong Kong. It's a few minutes from Mong Kok MTR station, and has plenty of bus stops just outside meaning you have quick and frequent access to the rest of the territory.
Saying that, if you're going to Hong Kong for dining and shopping, Mong Kok has a huge amount to offer for any price range and tastes.
The rooms are quite small so if you have a travel companion they should be someone that you get along with well. Also, if you are 178cm or taller you may find the bed on the small side. I could have my feet flat on the bottom of the bed and my head touching the other end. It didn't really bother me, but it is something you should consider.
However, despite the size, the room is very modern and clean, with a new air-conditioning which will come in use in the hot and sticky Hong Kong summers.
For me, after taking into account the cleanliness, modernity, location, and price of the room, the size doesn't really matter.