Honestly, if you are questioning the value of keeping a PC in your ride, then you probably shouldn't have one.
As Malcolm stated, a PC in your vehicle isn't as simple as install it and go. It requires maintenance, fiddling, tweaking, upgrading, and so on on a fairly regular basis.
It takes commitment at this point, as well as a lot of work to keep it up to snuff. If you're not wiling to commit yourself (with or without straight jacket

), then the vehicle PC hobby is simply not for you.
Lets face reality:
It is far simpler and many times less expensive to get most (if not all) the functionality of a PC in a high-dollar all-in-one headunit. There is also less maintenance.
In North America, there are lots of GPS nav software options. In other parts of the world, it's hit or miss. It sucks, but it's a fact.