I am all for supporting the products you like, but honestly as a business owner the bottom line is that it is more important to worry about what your clients think, and want to purchase than your own personal beliefs as to what someone should or should not use. If a client wants a retailers expert opinion then by all means give it, however it is just bad business to bad mouth the products you do not like: just do not endorse them. After reading his continual rants on their website about Shimano, PP, etc. I just choose to support someone more positive.
Although he does not have a Web presence, I Primarily shop from Joey down at Squidco because he has excellent customer service skills, he is always the cheapest, calls you by name, and will match Mark's Pricing on anything anytime. And he is a wealth of information!
As for Power Pro, there are fancier lines out there but remember that most of us are buying spectra for it's coarse kelp cutting ability. Smooth lines do not cut as good. Some of the other lines like JB, Izor, etc, are very nice for being smooth, casting quietly through the guides, staying knot free, and maintaining colors, but they are not quite up to par in the kelp cutting business. I have used Power Pro for more than 10 years and I have to say that I can only recall once that I cursed their line, and it was to be honest, probably more my line neglect than their product. And besides it is cheaper and more readily available than some of the other lines. Is it the best?... maybe not... but it works for me, and if it ain't broke... don't fix it.
Rant off...