As far as being farm animals, these sheep are excellent. They work well as wool sheep because they do not require shearing, they cast(shed) their wool each spring. The wool is highly prized by hand spinners for its soft texture and wide color range of browns and creams. Their meat is also starting to enter the specialty meat market as a delicate alternative to mutton. They are also an excellent means for managing pasture land. They will eat Scots broom, which is an invasive species in many areas, berry vines, and many grasses that other domesticated animals find unpalatable. They are often used as an alternative to herbicides and bulldozers for reclaiming land that has been overrun by brambles, poison oak, and other noxious weeds.
One population, the Hirta population, has remained unmanaged and as such is a good data set for scientific studies. This population meets many of the Hardy-Weinberg requirements including no immigration/emigration and no pressure to evolve due to predators.
Recently the population has come under the scientific radar because it appears to be shrinking. Each of the more recent generations has been smaller than their parents. Recent studies have shown that this trend and the variation around the trend are primarily consequences of environmental variations, due to climactic changes, and not evolution. The environmental changes have resulted in a reduction in lamb growth rates as well as less of a need for the large fat stores of the older generations which were needed for the harsh winters. These winters are becoming less harsh, thus the sheep have less need to build these fat stores.