I have tried a couple of their seminars (lighting and street photography) which were taught by capable teachers but clearly geared towards the beginners.
I'd say they are a good starting point if you're just getting to grips with photography, but there possibly are better sources of information and learning once you get to a more advanced stage. If you're comfortable shooting in the full manual mode, you probably do not need them.
A specific note about the lighting (external flash) seminar: terrific if you're just dabbling with hot shoe Speedlites/Speedlights on a Canon or Nikon camera, but of more limited use if you use a different, "exotic" system (Sony, Pentax, Olympus, Micro Four Thirds...) or if you're looking for more advanced tips - you can still ask your questions and get good answers, but most of the class will be devoted to more basic stuff.