Since DASH uses KUIP, you automatically obtain the many benefits provided by KUIP. This is the same interface package used by PAW, so even if you have not programmed with it, you may already be familiar with it. It gives you a command history (up-arrow) and command line editing. You can have MACRO files (.kumac). It has an integrated help facility.
A good command line interface is most helpful during the development phase of your analysis program. You are able to use the DASH commands to start up your analysis and analyze a single event and then interactively work with it. Using the CALL command, you can repeatedly invoke an event entrypoint, which can be helpful when debugging some code. Using PATH, you can include in the analysis path event-dump or other diagnostic tools. Using RUNLISTs, you can go right to an interesting event in a data file.
The transition to batch jobs which analyze large amounts of data is straightforward. The same commands you use interactively go in the batch file. Plus, the commands can be broken up into KUIP MACRO's- for example one might have MYINIT.KUMAC which sets up things that many jobs would want.