The Mexico City metro system is unlike anything else in the city - it is logical, orderly, user-friendly and largely reliable. There are the occasional breakdowns causing people to be trapped in the tunnels for minutes to hours or preventing your train from leaving, but I've only personally been delayed once.
This is Mexico City however, I doubt there is anywhere you could go that you could overlook that fact. A hallmark of the metro are young guys and girls with stereo-equipped backpacks blasting music to promote whatever pirate CD they're hawking - anything from cumbia to musica romantica to the Doors or the Beatles.
One of the odd things about the metro - to my eye - are the stores in the stations. Without fail, in every station, there is a Domino's Pizza and an alternative nutrition store. I particularly enjoy reading the advertisements on the nutrition stores, such as this one above. Offering include: Nopalinaza (Cactus/Linseed) to combat obesity, gastritis and colon problems, "Hepanat", effective in solving liver problems or bad breath, some sort of soy product that helps with embarassment, bad moods and sadness (not to mention ovary pain), creatine for muscle development, vitamins for kids and, the staple of every nutrition store and, I suspect, their bread and butter - "X-tra Virile" (100% natural) which helps with, well you can imagine.
I shouldn't laugh. I know that having the polis stand on boxes makes perfect sense surveillance-wise. But it does make me laugh, just like the polis on segways up and down Reforma.