Having many open windows on the desktop can lead to various usability problems. Window content may get occluded by other windows and working with multiple windows may get cumbersome. In this paper, we evaluate the idea to integrate stacking and tiling features into the traditional desktop metaphor. For this purpose we introduce the Stack & Tile window manager, which allows users to stack and tile arbitrary windows into groups that can be moved and resized similar to single windows. To evaluate if stacking and tiling can improve productivity, we conducted an experimental evaluation. We found that participants were able to perform various multi-window tasks and switch between tasks significantly faster using Stack & Tile. Furthermore, we found that the time to set up a Stack & Tile window group is reasonably low. Stack & Tile is open-source and has been used for over two years now. To evaluate its usefulness in practice, we conducted a web-based survey that reveals how people are actually using the new stacking and tiling features.