I had two new experiences on the metro yesterday.
First, after waiting longer than usual for a train to arrive, upon arrival there was a distinct burning smell. Interesting. I boarded the train when the doors opened and waited. The smell got stronger and the air started getting a little hazy. I looked out from the open door and saw thick smoke at the back of the train. I decided that this probably would not be resolved quickly and/or if the metro continued, the smoke couldn't be good for anyone's health, so I left. Still not sure what was burning.
Second, I took the new metro line for the first time. Construction started right around the time I moved to Mexico and its FINALLY finished and open to the public. I didn't have to go far, but wanted to use it to connect between two metro lines. I discovered that the transfer between lines underground requires a HUGE amount of walking. Though probably not the case, I felt like I could have made it to my destination walking above ground for all the walking I did just to transfer lines below ground. I'm sure this line will help a lot of people, with stops in areas that previously did not have a metro and connecting in the south of the DF four lines that previously were connected further north in the city. However, in my case, it doesn't seem like it will be as convenient as I had hoped as a "quick" connection to another metro line.