Mongkok Guest House is economical stay in a bustling part of the city. If you want a genuine HK experience stay in Mongkok, if you want a western style hotel stay, pay more money, stay at the harbor.
The room is small, it is the Sun Hing Building on Nathan Rd. It is clean, it has a private bath (also small) with shower that is not in a separate enclosure; this is typical throughout Asia. We were provided fresh towels everyday, trash cans emptied, and toothpaste/brushes/shampoo provided. The building has an eclectic mix of guest houses, businesses and residences and is in the center of the Mongkok business district. There are good locks on the doors and a kinda security on the ground floor. Out the backdoor of the building will reveal many eateries.
If you come from the Airport take the bus (A21); easier than the MTR and bus has no limits on luggage, no stairs, very little walking. Get of at Sino Center and walk South to the nearest pedestrian crossing. After crossing, the building is North.
Stay here as an economic alternative to the tourist hotels at the harbor. I found it to be quiet (24th floor), clean and I loved all the nearby food options.