I disagree...
I just took Tom Simpsons class, I've been shooting pool for almost 20 years, and his class has changed my game. You are given so much information about the game that you can't really retain it, unless you do as they say, which is take notes. I took lots of notes and I asked all the questions I needed to. But at the end of the day, unless you invest the time to run through the drills they introduce you to and focus on the fundamentals that they constantly remind you of, you will not improve. The aiming systems are also effective, you have to find your understanding of them for them to work and you have to run the drills while incorporating the systems. I use 2 of the systems almost 90% of the time and the other 10% I shoot with my eyes. I've improved considerably and it's only been about 6 weeks since I took the class. The class is well formatted, there are 4 instructors all walking around and you can get some one-on-one as well, but if you are an experienced player, they will make sure you got it and then allow you to get a feel for it and check back, while focusing more towards the less experienced players.
I'm sure any other pro player that is giving lessons is very good too, I can't knock them and I may even check one out for some one-one-one, just to add to what I gained from Tom Simpsons class, and like his class, I will work just as hard, because no matter who is teaching, if you don't put forth the effort, then it will seem like it wasn't any good.
Finally, I would recommend Tom's class if you want to learn more than you could imagine about the game, because the amount of knowledge that is given can benefit anyone, especially if you've hit a wall in your game. You will not retain it all so you must take lots of notes, the good thing is, he gives you a book that has everything he teaches in it and plenty of space for you to add notes, diagrams, or whatever and you can look back later to refresh yourself. And you can send emails later to get more info or get clear on something if you need to. My love for this game was already great, but now, because I know so much, I can't stop thinking about it, I want to play all day and all night and I'm confident I can compete with anyone at this point...