I must agree Federer is currently playing the best tennis since he started to decline.
Can you picture Roger 2008-2010 beating Nadal at Indian Wells? Because I can't.
I believe Fed is enjoying a sort of short-term Renaissance of 2004-2007 form.
Part of it is because Federer learned how to play Nadal in 2009 and has been adjusting his tactics against Nadal bit for bit ever since, but he is not good enought anymore to constantly challenge the peaking NAdal. I belive he is 4-5 against Nadal since 2009 and has only played a really bad match in Miami since then. Federer's backhand is alot better since 2009 against Nadal but not so much against everybody else.
He is doing well to get the most out of his 'old age', but he still can't cut it against Nadal in slams. This is proof that Nadal hasn't really declined like some say. I agree that Federer has improved his backhand somewhat, but he lost a bit of speed, his back doesn't hold up as well in the long run and he's lost his mental edge, especially in slams. These 3 are clear signs that Federer is declining.