It's a fact that inexperienced pilots refer more to information (like the FMC) than experienced pilots when performing the same task.
For me starting on the 737NG, it's been a great help to "draw" circuits and expected radar vectoring approaches. For a visual approach, it's great when flying manually with F/D off, to be able to scan the V-NAV path, so you have a better clue about your distance vs. altitude during the approach. Furthermore it helps you flying impressive "glide in" visual approach, without adding thrust before maybe a 1000' AGL. Because of the fact that the V-NAV path is the aircrafts idle descent path.
For radar vectoring approaches, it gives you a descent planning which is more realistic and therefore a save of fuel costs. So instead of flying around in 2000' using a lot of thrust, like I see a lot of people do, you can put yourself quite perfect for a glide in approach. It also gives you decent with a lower chance of the use of speed brakes.