In my country is deffinitively approved. Now, I must say it's not seen as a major change. But people is pleased that, whatever the case if it forced you or not, we see now all kinds of strategies.
I rarely use it since I'm with the philosophy that you should use it only when your opponent has a one-way team AND if your opponent is comprehenively much better than you. If my opponent has a worse team than mine, even if he only plays one thing, I don't use GDP: basically I don't need it to defeat him and I take away from him the tactical option of surprising me and maybe, you know, an injury here or there to my tough guys and/or foul trouble, and suddenly he's in the game and maybe he has a chance to beat me.
And if the guy is better than me an plays everything and has a complete, balanced roster, what can you do? No GDP will save that game and if you miss the prediction -which is the most probable chance- you might end up losing by a large margin, which could be trouble for a tiebraker in the long run. So in that case I take my defeat in a humble way, don't use GDP and go home with -10 or whatever the difference was.
My advice for managers in D.II or D.III would be: use it, only if need it. For D.IV, I don't know very well the strategic subtleties, since in D.IV very few skill lvls of difference can make a bigger impact in the game that in D.II. So perhaps GDP has a more powerful use in the outcome of games in D.IV or lower, where a Center with 7 in passing can have a massive impact against a Center with 5 in passing than in D.II, where that subtlety, although not meaningless, could be squashed if your Center shoots 17 IS against his Center defending 12 ID. So if you're playing inside [either LI or LP] basically you don't care about passing for Center.