I came around to Zero ADV because I realized that it is only REALLY useful... I know MikeT23 has said this a number of times... IF you are trading for other teams' prospects, players you have NO background on.
Everyone seems to say "once you get used enough to the ratings to make your own projections, you don't need it." Well, I'm not really... but I agree with Mike, once I draft players I know the ballpark their numbers are in. I expect this guy or two to make the Majors, these guys aren't ever going to get past AAA, etc.
The next thing is that I play in a world with a lot of experienced managers who seem conservative in their game play. That means that almost NO top prospects move in trades. Sandwich picks seem to move easily, top half first rounders almost never. In our world even free agency is kind of dull, it's rare to see Max Contract Studs. So with the predictability of the draft and IFA processes, I can pretty much evaluate players based on their Draft page (or Contract page for IFAs), current ratings, and age/experience.
Now, if you play in a world that's more unpredictable... owners who gamble more, or make more outright blunders in player evaluation and drafting... I suppose things might be different. But I came to the conclusion Mike's talking about, money spent on ADV can be for no reason other than to confirm your own bias about your players.