First off, I didn't read all the replies, and I'm all for using whatever training system works for hypothetical-you and your horse. Whether its sticking to a brand-name trainer-in-a-box or drawing on a hodgepodge of accumulated wisdom from many sources, if you're getting the results you want, I say run with it.
The majority of the problem I have with the Parelli system is that I honestly do not understand it. I can read a Parelli description of something very simple, say, driving a horse forward on a lungeline, that I and my horses know and can do as automatically as anything can be with a horse, and I literally have to read it 2-3 times before I can sort out what on earth is going on. They've truly reinvented the wheel. Dealing with horses is not rocket science, and they are not that complicated. That being said, I'm sure there are people for whom the Parelli explanations make more sense and clarifies the task, so that all evens out in the grand scheme of things. Just because I personally understand other BNT systems or non-BNT explanations easier does not make Parelli "bad." It just makes the system "not for me." My horses and I get on fine and dandy.
I think the overall problem is bigger than any one tv trainer or boxed system. The problem is the widespread idea that any joe can learn horsemanship out of a box. I'm a huge fan of horsemanship tv shows, books, and DVDs - they are a fantastic resource, and as riders, owners, and trainers, we're lucky to have these things available. But the issue is that they are a resource, not a substitute for in-person guidance by someone with experience doing what you want to do.
Trainer-in-a-box systems, no matter who's logo is embossed on the packaging, gives the impression that anyone, at any time, can do anything, with any horse, as long as you follow the recipe. The best a box system can do to rectify that is a trouble shooting section, essentially equating to a high-altitude variation on a cookie mix packet. Lots of people understand the importance of feel and experience, and compensate for these shortcomings of box systems, but at the same time there are a lot of people who do run into problems, and are left wondering why their souffle fell in when they followed the recipe to the letter.
A little bit of knowledge is a dangerous thing. A little common sense and perspective can be invaluable, whether your horsemanship knowledge is based on a BNT boxed method or a less systematized collection of exercises and concepts.
A stubborn horse walks behind you, an impatient one in front of you, but a noble companion walks beside you ~ Unknown