Next time I will chose again Regina
We stayed in this hotel for seven nights in February 2006. Its location is one of the best you can get in Madrid. Just in front of the hotel(10m) is Sevilla metro station, but anyway you do not need the metro because all the important places are walking distance(max 20 mins) from the hotel. Puerta del Sol & Grand Via 5 mins away, Plaza Mayor 10 mins, Prado & Thyessen 10 mins, Reina Sofia & Retiro Park 15 mins...
The hotel was very clean and the staff was ok. As bad points for the hotel I would mention the breakfast, which was the same in all 7 days: 2 types of croissants, 3 kind of salamis, 2 types of cheese, some fruit salad & kiwi, coffee, tea, milk and some awfull juices.
Another annoying thing was the isolation of the rooms, which was not that good and you could hear the persons passing in front of your door.
Also the price I have paid was very good much bellow the rates of other hotel and also under the rates displayed on their site.
In conclusion, when I will go again in Madrid as a tourist I will definetely go again to Regina Hotel.