can offer a little, spent 2 days and nights there about 5 years ago. Hotel Carlton as I recall which was reasonably priced (or I wouldn't have stayed there!), and had nice, spacious (for Europe), and modern rooms. Not so sure the meals are good value though, probably want to eat away from hotel. It is located abt 5 mins walk from Atocha railway station, and 10 - 15 mins walk from Prado museum (though IIRC this and other museums tend to be closed on Mondays for some reason). Also near Prado museum is a stop for the Hop-on Hop-off bus, which covers a reasonably generous portion of the city and was fairly priced.
Anyway, the Carlton is one of hundreds, so for reviews on many Madrid hotels follow this link and type madrid hotels in the search function field www.tripadvisor.com
Oh, and 2 essential phrases in Spain - cerveza fria (cold beer) and vino tinto (red wine)
One tip is that the train is a very easy way into town. Wish I'd caught it as I was ripped off by my taxi driver. Nice as he was, he gave me about 15 Euros less change than I was due - I didn't realise til after I had checked into my hotel. Very sneaky.
On my departure i worked out the subway and it was great. I suppose I saved some money there - so it balanced out.
Always be on the ball is the moral here and don't rush transactions. Especially when jet lagged.