Federer is a very good volleyer, but obviously not on the same level with Edberg, Mac, Pete, ect. He does miss some easy volleys, but I mainly see him do that against Nadal, where his play sometimes seems puzzling. Nadal is a huge match-up problem for Federer, but it still puzzles me why Federer attempts certain styles of play against Nadal. What's more is that Federer seems to have a very negative mindset in playing Nadal that he has against no other player.
For example, Federer was up 7-6, 1-0 and he failed to hold serve, somewhat inexplicably. Federer was also up a break at 4-3 in the 3rd set and he again, failed to hold his serve, yet seemed to hold his serve routinely for the rest of the set. To me, these are the moments where he loses the match against Nadal. If he could just get a little bit of steam, I think he'd have a shot at beating Nadal in a major, even at his age, but he also seems to falter at the key moments.
I agree with Strobe Lights that Nadal rarely has to hit tough volleys. That said, I also agree with PC1 that Nadal could have found his way into net a bit more in the final and I only think that can help him.
As for Nadal's serve, it's the ultimate percentage serve and it's bloody brilliant for clay-court tennis, but for a lefty, I think he does need to make better use of the lefty-serve out wide. I don't think there's anything wrong with his timing, as Limpin writes, but I do think the technique isn't the most fluid and is somewhat of a "muscle" serve as Limpin also writes.
Nadal is a percentage player, at his heart, and I just don't see him being able to make adustments to beat Djokovic on a regular basis.