While now I work for SAS as a JMP systems engineer, I'll answer from the perspective of my former role as a statistician at my former employer, Eastman Kodak Company...where I was a JMP user since version 1. By JMP version 3, I never touched SAS or APL again.
What is JMP?
Among many areas of application, JMP was the data analytics and DOE desktop platform of choice within our Six Sigma Black Belt training curriculum. Hundreds of Kodak Six Sigma Black Belt candidates around the globe were trained using JMP. Hands down JMP offered the broadest and deepest deployment of quality and statistical methods in a way that did not constrain us wrt to topics, methods, and ease of interacting with their colleagues on the thousands of Six Sigma projects that were touched by Kodak Black Belts.
What does JMP do for you?
During my last 8 years as a supplier quality manager I used JMP almost daily on a variety of quality and process improvement projects in collaboration with Kodak suppliers across the enterprise including finance, customer service and support, manufacturing, research and development, marketing, IS/IT, logistics, etc.. These projects delivered millions of dollars of savings to Kodak and our suppliers through reducing defects, process or product variation, cycle time or lead time.
It was not uncommon that during any one supplier improvement project, supplier members of the team would see me work with JMP and ask, "What's that?". I'd answer "JMP...a desktop statistics program from SAS." And quite often...they'd ask, "How do I get ahold of that?" So I actually helped sell a few copies of JMP to these folks over the years too!
What feature can't you do without?
The DOE platforms in conjunction with the Fit Model sub platforms for the Prediction Profiler, Simulator, and Contour Profiler. These platforms told us pretty much everything we needed to know in manufacturing and R & D. What should our process set points be? What product variation can we expect? What is the shape and form of our process operating window.