Finishing the tops of interior walls and windowsills with drywall gives them a clean, modern look, but is a difficult process that adds greatly to the cost of plastering. Our compromise was to have the builders leave the edges unfinished, and we would add wood caps ourselves. This let us vary the materials by location; the kitchen windowsill above uses Valchromat, eco-friendly colored MDF that will coordinate with the drawerfronts.
The burnt poplar we installed on the office walls matches the floor grid:
as well as the stair railing (nail gun holes can be filled with a wax crayon):
In the bedrooms and bathrooms on the upper floor, cypress caps top an interior wall that completely covers the foundation. This creates a foam-insulated barrier around the cold concrete (as well as a handy shelf).