Wind energy has many advantages but there are some possible downsides, including: intermittency, initial costs, wildlife impact, noise and appearance. These downsides can be broadly categorized as technology, cost and environmental impact.
Wind energy only works when the wind is blowing at a sufficient speed. Energy is hard to store, so other forms of energy need to work in concert with wind to provide consistent reliable power. One advantage for wind compared to solar is that wind power is not based on time of day.
The cost to acquire land, install turbines and build other infrastructure is high compared to some other forms of energy. As turbine technology has improved, the costs to install and operate wind farms have come down to a rate that is competitive with other forms of energy. Efficiency is achieved by grouping many wind turbines together in high wind areas.
Wind turbines are big, and up close they are noisy, and to some they look ugly. These issues are inherent in current wind technology, so locations should be selected that conform to community standards and impact the local environment the least.
Finally, wind turbines do kill wildlife. Studies have shown that birds and bats are at risk, but the impact varies widely across wind-resource areas. Studies are ongoing to determine the factors involved to try to minimize the impact.