I would have to say the item...
I would have to say the item that to me is most outstanding about this hotel is the service level. It is a very small hotel and the staff are very hands on.
The manager waited until I had arrived to make sure everything was ok (I arrived at 11:30pm!).
Another time, I wanted to buy some insect repellent, the manager actually walked me down the block to the pharmacist to make sure I was buying the correct item.
The location of this hotel is excellent, with just a 1-2 minute walk and you are in the old quarter with all of its restaurants etc.
The one downside I would say to this hotel, is that even though they have quite high quality windows that do cut down on the noise (i have built houses before so I can judge this well), there is still some street noise. I however do not know of any hotel in this price range (near this location) that would not allow street noise into your room in Hanoi.
This hotel offered me an airport pickup, I did not take it, but in hind site I would, as the price of the airport pickup is the same as the flat rate taxis from the airport, and many of these taxis do not seem to know the smaller hotels in the city that well.
I stayed at this hotel again after doing a 3 day tour to halong bay, leaving my luggage with them (for free) without any problems.
In this price range, i found the hotel excellent value for the money. Note also, that though asiarooms says breakfast is not included for the single room, mine was included.