First off, the men: Are we seeing Roger getting old? He seemed a step slow getting to those deep baseline shots, and didn't seem to create the angles were are used to seeing from him. I don't think we are seeing an end to his greatness, just his dominance. Traditionally, Roger has been a great tactical player, but not so good strategically. The difference is the approach to the match: some players try to impose a certain style or will on the match that makes it difficult to play them. Brad Gilbert is famous for teaching this style. I think Nadal and Murray are great examples of this. I can't really put a finger on how to describe it, but it deals with their overall approach to each match.
The counter to this is a more tactical game. Federer has refined every aspect of his ballstriking, and can react to his opponent better than almost anybody. From point to point, he doesn't really lose his cool, constantly keeps the pressure on, and consistently hits great shots. He doesn't try or press to play a certain way, but just tries to hit the best shot at every possible opportunity.
How does this explain his decline then? I think that as a player ages, it becomes harder and harder to play great tactical tennis. I mean, you look at Agassi: I think he was able to be successful at late stages in his career because he made sure that the matches went his way, knowing that he wasn't fast or powerful enough to hit the crap out of the guys he was playing. He's a guy that would make you hit one extra ball for a winner, and that would get under some guys' skins. I don't think Federer is that type of guy. I think you can kind of have your way with him, hitting some big shots, but unlike in the past when he would take your big shot and turn it into an insane angle, I think more and more guys are able to get balls past him. I know Fed is famous for not using a coach, but at some point, I think he needs to switch to a strategic game, which involves match planning and the use of some outside perspective. You make the call.
Now to the women: I love it each time someone new supplants Serena as the woman to beat in tennis. I mean, she has spent some time away, she's had a few injuries in year's past, but she has absolutely dominated the last decade. I don't buy that Henin is better. We know that Sharapova isn't as good. After Graff, she became the transcendent female tennis player, and regardless of what you think of her personally, she is the best.