I think I remember electric trains were in Berlin (Germany) in the 1880's. I think they are great for cities. Although some may say that it just transfers the pollution to somewhere else, thats not a bad thing. The centralized pollution from a power plant "over-the-hill" doesn't clog city air, and its easier to add upgrades that make the plant run cleaner.
Once I was forced to use the light-rail in Los Angeles, and I was pleasantly suprised. They kept it cheap enough (and city parking expensive) so that a certain percentage of commuters stayed off the streets. I also was very happy with the light-rail system in San Diego and Manhattan. I was very disappointed in the San Francisco bay area, it seemed like a chain with many links missing.
For inter-state trains I still think series-hybrid diesel-electrics are doing a great job...