Yes, there are a lot of opinions about windmills. More and more towns are coming up with regulations about them, so if planning to install, please check first to make sure you will not run afoul of a regulation requiring you to take it down after built.
I am a strong supporter of windmills (besides being a retailer of windmills at
www.sustainabilitynh.com, based in Laconia), but in general, NH is not a good location for residential windmills (in terms of being cost-efficient). Windmills do best with wind that blows close to the ground without obstructions. Iowa (where I used to live) is a good place for wind - wind comes off the Rockies and blows close to the ground for hundreds of miles. In NH, the hills break up the flow of the wind near the ground, and the trees add lots of turbulence to the wind, making the wear on the windmill more intense.
The large (commercial scale) windmills have been implicated in some deaths of birds - it is an issue; but smaller wind generators will not provide much of a hazard (and the spinning ones even less). It turns out it is not the collision with the blades of the large windmill rotors that is the major problem - bird usually avoid the blades. It is that the large blades create a low pressure zone just following the blade, and when an animal (bird, bat) flies into it, their inner cavities and blood vessels can burst from the sudden near vacuum (according to autopsies of dead birds and bats). Small residential wind generators don't create a big enough low pressure area to injure the animals.
The same rebate available to solar electric installers is available to those who install wind power. There is a 30% rebate - off your next years taxes (not off your taxable income) from the Federal Government. There is an up to $6000 rebate from the State of NH, and if you are a grid tied NHEC customer, there is a rebate of up to $3,500
I would agree with jmen24 that solar hot water (and solar electric) are both better deals than wind power in NH. We get more usable sunlight in NH than almost anywhere in Germany, which produces the most solar electricity per capita in the world. Sure we get less than California or Arizona, but we also have the advantage of a cooler climate (esp cold winters) which means we produce more electricity per hour of sunshine with the same solar electric panels than they do. With rebates, solar is now cheaper than the utilities over about 20-25 years (and that's not including an factoring in of increasingly expensive electric rates over the coming years.
In NH there are relatively few places where wind by itself will be economically feasible - lakefront is one, where wind blows across the lake toward the windmill. Ridgetop without trees is another. Some funnel valleys are also good for windmills.
If you are thinking of installing wind power, first, measure the wind for a while. While you might have three or four months of good wind at your chosen location, it might be not very good the other eight months of the year. Another difficulty about wind is its unpredictableness. You might measure the wind at one location and decide it just isn't a good location. But because of the lay of the land and the way the land channels the wind, it is possible that a spot just 100 yards away is an excellent site for wind. The problem is that it is very hard to tell from just looking at what are good sites for an invisible commodity.
The general rule of thumb is that your wind generator should be located 30 feet above any obstruction within 200 feet. In Iowa, that means building a 37 foot high tower so it is 30 feet above the corn. Here, that might mean an 80-100 foot tower, which are A LOT more expensive than a 37 foot tower (another reason why it isn't very feasible in many locations in NH).
There is one situation where a windmill may work well in NH. If you have an off-the-grid home and are using (and entirely dependent on) solar power, the winter months are the toughest, as sunlight is on average 60% less than summer. A wind generator USUALLY does best in the winter months here, just when solar power is at its minimum. So a windmill complementing a solar installation allows you to downsize both and find a practical balance.
As to the sound windmills make, that is primarily a problem with "propeller windmills", with the turning propellers. The type of windmill pictured in Reply 9 by Just Sold produces very little sound. Additionally, these spinning turbines pick up power better from lighter winds. For residential applications in NH, I would recommend them over the propeller systems (though Sustain Ability can order and install both types). I myself am planning to build with a spinning windmill as a back-up to off-grid solar next year.
On the commercial scale (300 foot high windmills) NH is an excellent state for wind-power - on ridgetops; but for residential size, there are surprisingly few places that are economically feasible in NH. I know this is not everyone's primary consideration. Whereas Solar Power (with rebates) is cheaper than buying from the power company (over the life of the system); wind power, even with rebates, usually will not break-even compared with grid-power.