The fancier rice cookers monitor what's going on inside and turn off when the last of the liquid is gone. At the lower end I do not like them because that ends up somewhat overcooking the rice next to the heating surface--I prefer putting it in the microwave using settings I have determined by experiment to work. Perfect every time.

I presume the more expensive ones are better at avoiding overcooking but it seems to me hard to conceive of a conduction-heat system that doesn't suffer this problem to some degree.