When you buy software, all the brochures talk about what the program can do, but they never tell you how long it takes to do it on the monitor. Much of what the software can do takes more time than it would have freehand. Of course, it is ultimately faster. The computers in our office have helped us to be able to do a million dollars worth of work with the same number of people. That's where it has been useful.
Portability is another shortfall.
I can draw anywhere, anytime and on anything. With laptop technology consistently improving, however, soon it will be possible to carry the necessary CAD power with you. A. First, take enough time to find software that works the way you work. Buy the best hardware you can afford. Skip the plotter and get more raw power.