Don't let the small size of an RV or mobile home put you off. There are lots of ways to make the most of living in a small space.
Firstly, it seems that many RV dwellers are alike in the fact that they really don't spend much time inside. While they value having the cover quarters to sleep and bathe in, most spend the day under their awning, or out and about exploring whatever community they are staying in. It is obviously easiest to spend more time outdoors when you're in a warm climate, but considering that warm climates are the usual destination for RVers, this shouldn't be a problem.
In a smaller space, you need to maximize efficiency. This isn't usually hard in RV's, as they are built with plenty of storage niches and double-purpose furniture - like tables that turn into beds, and cupboards in every tiny empty space available. You can help minimize clutter by assigning a place for everything, and putting things away as soon as you're done with them. Also, make sure your appliances aren't redundant. In a smaller kitchen, there might not be room to put a microwave, toaster oven and toaster all on the counter. Choose which appliances are most important to you, and consider getting rid of the rest. Do you need a food processor and a blender? Probably not.
Also, consider putting all your electronic equipment into niches or cupboards. On counters and tabletops, electronics can take up so much space, and become the visual focal point of the room. To further minimize the spatial impact of electronics, consider things like TVs with built in DVD players, and other two-in-one appliances.
Consider that cupboards as storage space will make your RV appear far more tidy than if storage is on open shelves. Consider this when you are choosing a model, or making any renovations to your RV.
With a little conscious effort, you can make the most of living in a small space, and enjoy RV living to its full potential!