Ugh... I could answer to 97269236543765435 points of that blog above, but I will use my time to other things. Besides from repeating the obvious -- the guy is technically better -- and there are no pills to that, I´ll just answer the serve part (because the bh part the guy answered himself):
If I wanted to find doping evidence on the serve, I would look for the average speed -- and that every tennis fan knows that has dropped in Federer´s case. His serve always had a very important placement component, and it is just getting better. The serve is a technical aspect of the game, sometimes hidden by the fact that some big servers just slam it down. This year Federer is firing some second serve aces, just out of placement. I guess only those are enough to explain that 2.2 aces differential the blog author cited.
Anyway, I just disagree with the guy. But there is one thing I agree with him: that you can make those claims if you think you have a point. I know that accusations are dangerous thing, but one can say that in his opinion player X is a doper (I wouldn't do that, but still). I am not offended by the fact the blog's author thinks like that -- and I do not think the big 3 + 1 are saints above any suspicion. As Darth always points, all those guys have the incentive to dope... but to equate better results to doping is quite simplistic to my eyes.