We arrived in Barajas (Madrid) on the 4th of November around midday and I called Aerocity from the airport. They came in only 10 minutes and took us to our destination (a little apartament near Plaza del Peru) with the fixed fee for two persons. We wanted to hire Aerocity for the trip home on 13th of November and a very useful information is that you must call them 24 hours earlier to make the reservation.
So we took a taxi from Gran Via, we were a little late because of the great nightlife . And we had only 4000 pst so we told the driver that we couldn't pay more. And he accepted and actually he turned on the meter and the price was around 3000pst!
Anyway in Madrid we took taxis about four times during our trip and every time the meter was turned on and we didn't get ripped off even once. We spoke with the first taxi driver about the price as I read on this board, but he replied that in Madrid the meter is always functioning so the price is not negociable. And, as I said, we didn't have any problems with the taxis and I think that 95-150pst/km is not much in a big city like Madrid.
We took the buses, my favorite because I got to see the surroundings and the city on the window (705 pst for 10 tickets which are also for the Metro) and the Metro is a clean one in my opinion.
Another information is that the stations are usually very close to each other so if you miss a stop you can always get off on the next one without having to walk much.
And the only problem was the traffic jams at any hour (even at 10.30pm) and the interminable waitings to cross the intersections. The Spaniards have a habit to go on after the yellow lights are off; after the red lights are on about 4 or 5 cars still enter the intersection so they are blocking the perpendicular road so the traffic is stucked on this one. I think that it's a deal between the citizens and the Police, they don't receive a ticket if going on on the red lights right after the yellow lights are off. I don't know if I made the things clear, but this was the one thing which suprised me.

The Spanish have a flexible attitude to minior laws, especially those involving traffic. They say in Malaga that crash helmets are used for protecting the elbows!

well, I love this atitude too
cause our country is full of traffic policemen which give you tickets for every little mistake and I hate them
they are stupid too