I have one. It performs as advertised, that's for sure. I can slap on a coat of Collinite paste wax 1,2, 3. I use it on one car, three times per year.
For me, its overkill. I don't need to do paint correction. A Harbor Freight thingy would probably work fine. In my defense, they didn't have those when I bought mine, so it was do without, or pay nearly as much for a Porter-Cable. Also, good sealants are so long lasting and easy to apply, that the need is not so great.
If you are going to do even a few cars on the side for money, I would definitely say its worth it. If you have two good cars to take care of, I would say its probably worth it. If you have only one good car to take care of, I would say its worth it if you want to go the extra mile. This is the definitive machine. If you can't get it done with a Flex, you can't get it done. Bear in mind that at trade-in time you will more than make up the cost of the machine. If you are the type to run your cars into the ground, the Flex maintained car will be worth that last repair that keeps it on the road for another year. That will save you a lot of money, too.
Not to be morbid, but take into account your age. If you are not a professional and over 45 years old, this machine will outlive you.