Light Spill
The report talked about (and also linked) in the article above examined pilot projects, and makes the case for the economic sense of converting to LEDs. Among important points it considers is that LED lights will increase in efficiency, and decrease in price, at least over the next several years.
Most large and medium sized cities run pilot projects to test how such a change would work for them - what real energy savings there are, relative ease of conversion, cost of maintenance and disposal. Most responsible managers of cities, especially now in times of budget cutbacks, phase-in such installations only after a pilot study, and usually as part of standard equipment replacement. Even so, you might take the report itself with a grain of salt: it was sponsored by Phillips and HSBC.
One aspect of upgrading lighting seldom considered is to reduce light spill both into the sky above, into adjacent housing, and into the urban habitats of birds and other animals. I don't think, however (as a previous commenter suggested) that LED street lighting would cause additional negative health effects. We're exposed to street lighting only briefly, and usually indirectly, and in nowhere near the intensity of daylight.
