Sometime ago I would have agreed with you re the use of the head over the computer, and I still believe that all crewing officers must be able to calculate last lands etc by hand, however, if you are working in a very intensive operation where time is at a premium, the calculator is a very useful tool,reduces the risk of error and does save time.
Caution though, if your FTL scheme has any differences from the base of 371, then they should built into the program.