yea i have alot. i use solid works(roommate had it for his mechanical engineering class, so i swiped a copy...)
its extremely easy to use. from what i remember about autocad, its extremely difficult to use.
it also helps if you have some drafting experience. ive been using pen and paper since freshmen year of highschool, and only very recently moved into 3d cad for tthis kinda stuff. ive used it on other things before tho.
its great if you are building your own case, etc, but for stuff like dash fabs, thats more of a get your hands dirty job. all the planning in autocad will do nothing to get your bondo right, or help you sand.