I have had an in person lesson from GG and have his subscription. He knows his stuff and provides a ton of information on the site. If you are really trying to get a better understanding of swing and get good drills, faults and fixes, etc. to help improve, then I think the subscription can be a good resource. You can also upload video of your swings to a forum where two of GG's proteges will provide analysis and feedback and tips on what to work on.
My personal opinion is that his philosophy is to dumb down the swing and focus on the root problems, not just trying to find bandaids. He has some verbiage and terms that may make it seem complicated and may not resonate with everyone, but he basically focuses on getting a good unrestricted turn on backswing, dig the lead side of the pelvis down (which gets weight forward and allows you to be able to use the ground) and then push from the feet to rotate properly through impact (the feet are essentially pushing in operate directions which causes your body to rotate). If you do these things, you will have solid impact positions and club will properly shallow.
My experience with local PGA type instructors is that they tend to focus on and try to give bandaid type fixes, rather than fixing the root cause, which ultimately limits your ability to really improve over the long term. As an example, the issue I have battled over the years is an early release/losing angle too early in my downswing. I went to a well known instructor in Houston and he correctly identified the issue, but his fix was to simply focus on trying to hold off the angle through impact by doing half swings and then graduating to full swings. This helped a little but ultimately I was limited because he never focused on the root cause, which in looking back at the videos were getting improper pressures on backswing because of sliding rather than properly turning and rotating which then led to sliding/pushing weight forward in the downswing and stalling out. As a result of this, I had no chance of being able to rotate through and maintain the angle properly, but this instructor never even mentioned or discussed any of this.
I went to one lesson with GG, and he immediately noticed the same issue but focused on the root causes. Once he got me to rotate better in backswing and not slide, etc. my angle/early release issue was fixed (I still have do a lot drills etc to replicate the pressures and rotation consistently and properly and to overcome years of doing it wrong way but the lesson showed I am capable of achieving it).
There are definitely other instructors who could do the same, but as I have gone down the rabbit trail of trying to learn more about the golf swing over the last year or so, I have realized that a lot of the local PGA types are likely not as well versed on swing as people might think because it really takes a lot of studying on biomechanics, etc. so definitely exercise caution before selecting an instructor. A lot of the more well known guys, such as GG, Monte, Malaska, etc., do their homework and are constantly trying to learn more info and they actually tend to teach most of the same philosophies, but just have different feels, verbiage, or ways to communicate it so one might resonate more than the others.
Also, for the record and as a reference point, I am a 3 handicap and have been as high as a 6 over the last couple of years.