I know, another thread about this.
I'm convinced that Fed's new racquet has not helped his game, in fact his game has suffered. Sure, his age has played a role too. Even so, it is not a fault of the racquet!
Federer, to my knowledge, has never played competitively with a larger headsize than a 90. He even played with the Pro Staff 85 before switching to the 90. For him to go to a 98 is a huge break from what he forged his Pro game on and what he is accustomed to playing competitively with.
Players like Djok, Nadal, Roddick, Agassi, Pam Shriver, Chang, Safin all used larger headed 95+ racquets and were accustomed to playing with them and molded their games to these racquets in their formative years, just like Federer, Courier, and Edberg. For them to switch to a racquet smaller than 95 would be detrimental, as would the latter to a significantly larger.
Of course hindsight is 20/20, and sometimes you can only discover things after you've tried them. Such is the case with Fed now. Just my opinion.