I really like Room mate hotels. Good design, beautiful rooms and reasonable prices. This room mate is gem! Especially if you have a excecutive room. I had room 209 and it was AMAZING! Two balconys and you can see Teatro Real from them. Really beautiful room, nice staff, who speaks perfect english. Everything you need for perfect holiday in Madrid.
Metrostop Opera is right on the plaza and you can walk easily to Sol, Mercado de San Miguel, Plaza Mayor, La Latina, Palazzo Real or go with metro to Lago. Reasonable prices.
This will be my hotel when I return to Madrid!