How about specifics? Do you think teams actually use their grades on a player in a given game to base decisions on, for example, who to start and who to sit? Who to draft? Who to trade for? What data do they actually use from PFF?
How do you answer the criticisms of their data, in that the grades they give players are complicated by not knowing the play call, not knowing the assignment, and such?
Other wise, your statement that "they're good at what they do" comes across simply as you slavishly upholding another media-related site as faultless.