Nice! Looks like you could have even gone a bit heavier handed with it than that and gotten away with it.
Sharpening basically helps define the edges of objects in the picture. You have to be careful with it, though, because if you go too far it can have some horrifyingly bad effects... and if you go too far but not so far as to be blatantly obvious, you can wind up with halos around objects.
Nearly ALL digital cameras require some sharpening in post processing. It's a result of a necessary process to convert an image into X by Y dots. They put a physical antialiasing filter over the sensor that basically blurs the image ever so slightly in order to smooth the transition in color from one pixel on the sensor to another.