The largest and most powerful wind turbines produce about 5 MW. Most of these are produced by GE in South America, where oddly enough there are little to no environmental regulations. The turbines are made mostly out of carbon fiber, not an easy or cheap material to manufacture. All things considered, the energy required to produce and install wind technology is greater than the turbine is likley to ever produce in it’s lifetime. Take into account the emissions produced from the manufacture of the "green" machine and you’ll find that it exceeds the offset of the clean energy. Look at areas where wind energy is extensively used and you will find that all traditional energy production methods are still in use at the same capacity. This is due to the complex nature of elecricity on a large scale or grid. Voltage control, peaking load, and VAR’s are just some of the factors invoved. Wind energy carries a reliability problem because it is only produced when the wind is blowing, not neccesarily when it is needed. It’s getting better, but not quite there yet.

Visual pollution:
- put them out at sea
- build fewer, bigger turbines (the blades also go slower, so less obvious flickering)
- put transmission lines underground

Support for wind power in the UK is around 80%, if I remember my opinion polls correctly.

Wildlife:
- bigger turbines getting more power with slower turbine blades and less area.
- don’t put them somewhere stupid like an endangered species’ breeding ground!

The advantage of wind is that, across its life cycle, it kills very few birds relative to some other power supplies according to some studies:
http://www.spp.nus.edu.sg/docs/fac/benjamin-sovacool/Published%20Papers/Sovacool-Contextualizing_Avian_%20Mortality.pdf

I’m almost certain Bob J is wrong. A 5MW turbine weighs a few hundred tonnes. At 30% capacity factor and a 25 year life it will produce enough to make about 380,000 tonnes of steel. According to this:
http://www.energysolutionscenter.org/heattreat/metalsadvisor/iron_and_steel/overview/energy_consumption.htm

Life cycle assessments typically estimate the time taken for the turbine to produce the energy used to make & install it to be about 6-8 months.

There’s still a lot of unknowns about the effects of large scale wind power production. In this month’s Scientific American, they talked about global warming reducing wind speed significantly and since wind power production is geometrically proportionate to wind speed, this would be a sharper drop in power production. At the University of Calgary, they’re saying that if wind power production was to cover 10% of the land mass, the added friction would slow down the winds enough to cause a global cooling trend and the wind speed would increase. About all that we really know is that there will be some consequences, what those consequences are going to be is a matter of speculation at the moment.