PSI is headed by John Peterson. He was an instructor at S&W, then at SIG, and has now branched out on his own. He doesn't have his own range that I know of, relying on local ranges to host the courses.
I've personally had him as an instructor at S&W for pistol and sim's during one of the advanced courses. More recently, I took his defensive carbine course which was hosted at Nashua F&G last summer. My wife also took his intro defensive handgun course this past summer, also at NFGA.
I would characterize his style as stripped down, no-nonsense, here's what works. Unlike certain instructors who demand you do it their way and only their way he will quickly show you several ways, describe their pluses and minuses and then give you the opportunity to try them all. Then he gives you feedback and lets you continue with your chosen method (if it's working for you). This is an advantage and a disadvantage, as you do sacrifice some benefits of repetition. But that's what the advanced courses are for, to solidify your skills
His approach also tends to be high intensity and high value. He likes to cram a lot into 2 days since he knows most of his students can only afford a weekend or a couple of days off. At the same time he personally is very laid back, there is no "drill instructor" environment. Students get out what they put in, so you've got to be motivated.
He saves his war stories for the night-before lecture. Once you get out to the range it's shoot, shoot, shoot. High round counts are the norm (my wife shot 700 pistol rounds in 2 days). We did a similar round count during the 2-day carbine course.
John is still bringing his staff up to speed, and some of the instruction is a bit rough, but at his prices you can afford to take each of his courses twice and still be ahead of the game compared to SIG, S&W and others. The biggest issue is since he is an "independent" with no fixed facility, finding his courses can often be a challenge.