I have an industrial Pfaff straight stitch and a semi-industrial Bernina. I still use my home Pfaff for making button holes because it is easier than switching to the Bernina (different bobbin). I should use my Bernina more often, since it can also do a buttonhole, but I prefer the Pfaff for sewing silk and this is my only contract sewing at this time.
I bought the Bernina 950 several years ago because I was doing a false flat felled seam on wool, with a zig zag on the outside, for a designer in Michigan. This designer is no longer doing clothing for many reasons and I just haven't used the machine much recently. But- it was one of the best purchases I have ever made. The first time I used it, I was amazed at how fast I got my work done. I finished the work about 3 days early and just sat in my chair, a little dazed at the technology.
I love industrial machines, but I'm not sure everyone is ready for one. I waited too long, I probally could have used it earlier than I did. But I know people who have them and don't use them because they don't get the control they want. My repetitious sewing gave me the opportunity to gain a lot of control and I was ready to use the speed when it became available. I can't imagine sewing all the time now without them, some machines seem so slow they make me want to drool. Another bonus with industrial machines is the sturdy table, I find myself balancing with my elbows, and I could never get that much leverage with a home machine.
So how do you know when you are ready? I'd say if you can regularly sew with the pedal to the metal, even on curves, then you are ready. There are some places that will let you test drive, M.J. Foley here in Michigan has always offered when I talked to them on the phone. I've never tried it though, I made the decision to buy the Bernina 950 and they didn't carry it. And I purchased my Pfaff secondhand about 10 yrs ago, long before I was ready for it. It was just too good a deal to pass up for someone who had made up their mind to sew for a living!