I work part time in several race car shops and a trailer shop. The Miller plasma is really a valuable tool. We make patterns from 1/4 and 3/16 masonite and just cut the parts out. It works great for circles especially...we have hole sizes up to 6" that are used often and many other shaps.
I cut suspensions off trailer often. These are full of rust and grease and other not so nice stuff from horses and cows. Works great ans is fast.
We still use the O&A torch to heat nuts and for cutting the plasma can't reach.
One thing we found was that if you cut 4130 steel with the plasma the edge gets very hard and will kill a saw blade or drill very quickly.
I also use the grinder and cut off wheels extensively.
So all in all the plasma is just another usefull too, but not and end all.