I have an office in our house, but since I started renting a studio space seven years ago, my office doesn't get used as much as it used to. It might sound silly and wasteful that I rent a space outside of home to work in, but I had been working from home (first as a graphic designer and now as a photographer) for many years. It was too isolating for me, and the distractions of working from home are too irresistible. I like having a space in a building where other creative people are working, where we get lots of visitors, and I have gallery space so my work gets much more exposure. I find that I focus on work much more when I go into my studio than when I work at home.
So my office at home is underused at the moment. It is a great workspace but not really a great chill-out space or woman cave. The previous owners of the house had it fitted with built-in shelves, cabinets and counter space, so it's undeniably an office. There's no space for a comfy chair, but there is a nice big work surface that I use for framing and other bulky projects that are not so easily done in my small studio downtown.
There's not even a door to close, so it's not really a space I can use to retreat to quiet. Dogs, spouse, stepsons...anyone can wander in, so it's not much of a private space. I occasionally think about ripping out the built-ins, but then where would I put all my stuff???