Well, I didn't get to catch the match live, but I've just watched some decent highlights.
I'm really not seeing this unbeatable monster from the first 2 sets that everyone else is. There was a period of the 2nd set where he was playing that way but generally it wasn't much that I haven't seen from him before. Maybe I've been spoilt with Fed highlight reels from his dominant years and envision that level of athleticism and reliable firepower overcoming Djoker in some of these rallies when that is irrelevant to the situation.
However, he was playing to a very high level (as usual against Fed), with unreal defense and counter-punching ability (some gets were utterly insane) that would have required a huge performance from Fed, which he could only muster in the 3rd set. There was a decently long window of opportunity for Fed in the 4th set where Djoker cooled off, and the Fed of the 3rd set would likely have taken that set or pushed it very close. But Fed messing up on 2nd serve returns so often and making some surprising errors was very costly. Djokovic served great throughout the match and often does against Fed lately. Fed really does bring the very best out of him it seems, which is good for tennis.
First set taken off Djoker on Plexi though, which a lot of people have overlooked. Much of Fed's play really stretched Armstrong to his absolute limits, and if Fed can do that on molasses, then I'm pretty excited as to what he's going to be able to do on a faster court.
This is just the beginning for this optimist.