Nothing boosts a plants popularity quite like being named the Plant of the Year by the Perennial Plant Association. Calamagrostis 'Karl Foerester' was that plant in 2001, 14 years ago. Since then its use has proliferated to the point that its lost its edgyness.
But. Who cares.
It grows pretty much anywhere - although its ornamental value in the shade will be close to "none." Its tight vertical lines are always architecturally useful and bring a contrast to any border. The straw colorings of its seed heads take till mid-season to show - but to those of us who see browns as a color it is a quality go to.
Its widespread use I believe to be in the public and commercial garden - not necessarily home gardens, so there is still design terrain to explore for some. In the above image the grass is on a commercial site flanked in a entry planting by 'Woodwardii' Arborvitae and underplanted with Nepeta 'Dropmore.'
Landscape designer and Proprietor of Buffalo Horticulture