I disagree. I have seen this on almost every forum I have ever been on (this site being the weakest to support NLS).
I do not simply take any company's propaganda as fact. I suggest NLS, and suggest it exclusively, based on repeated success with many types of fish over and over and over again with almost no exceptions. In every situation the fish do better on NLS exclusively than anything else I have tried or seen them on.
IME the people who argue against it the most are people who have not truly tried it exclusively. If you have not tried feeding NLS exclusively for at least a few months IMO you cannot speak from experience. When people finally do break down and give it a try they become converts and just as 'extreme' as other NLS supporters.
We can argue about this day after day in thread after thread, but at the end of it all you cannot know how good it really is, or is not, until you try feeding it exclusively for at least a few months. Worst case you find out you somehow already had a very good diet and do not need to feed NLS exclusively. Your fish deserve this trial.