Very effective during my trip. It goes everywhere we wanted to go in the city! I felt safe even when it was late. Don't throw away your tickets until the end of the train trip. Frequent inspections occur, if you don't have it you could be fined. And some stations require the same ticket you used to enter, in order to exit.
The color and number coded system was really easy to use. Just find your destination on the metro map, choose the colour line or number that runs through it. Just use the end points (the last station name) of each line to find your direction, and then wait for your station name to appear.
Some stations are wheelchair friendly but not all. Lots steps so be prepared to use them. This is worth keeping in mind if you are traveling with large and heavy luggage bags or if you have mobility problems.More