Stain can be a wonderful addition to a hardwood floor. However, stain isn't suited for every type of wood and every type of home.
Adding stain to a home can have several different effects and change the entire look and design of the home. The key thing to remember about staining a hardwood floor is this; the darker the stain, the smaller the room will appear and the harder it will be to keep clean. Darker stains don't reflect natural light as well as lighter stains. This will make a room appear smaller and not nearly as bright. In a larger house, this really isn't an issue. However, if you have a smaller home a darker stain might not be what you are after.
Another thing to keep in mind while staining is contrast. A good contrast is key to completing the look of a home. If everything is the same color, it will be overwhelming to look at. For example, if you have darker cabinets then a darker stain might not look that good with it. The style and color of the furniture you own also plays a large role. Once again, contrast is everything, so make sure to pick a color that highlights the furniture instead of making it blend in.
Another thing to keep in mind is wear and tear. Naturally, a stained floor will show more scratching. Being that most woods are very light in color, if a scratch goes through the stain the scratch will appear "white" and really stick out. Also, repairs are not nearly as simple with a stained floor. Because the stain changes so much over time, the changes of being able to match that stain color exactly are very slim. It can be done however. On several occasions, I have mixed multiple colors to obtain a very specific color.
Moreover, the type of wood being stained plays a large role as well. Certain types of wood, (maple, fir etc) may appear blotchy when stained. It is always good practice to apply samples onto the area you will be staining and obtain the go-ahead from the homeowner. This way the client can see the stain color on their floor with their type of wood and lighting.