That blog is right about some things, but extremely flawed in many places. I'll give it a quick overview:
Characters: Dead on about Lelouch, I'm glad this at least is appreciated. Lelouch carried the show. I see little mention of Suzaku, though. I feel he is probably underrated. He's also way too generous with his "memorable" second tier characters. Out of that list I would only choose Cornelia (season 1), Lloyd, and Jeremiah. The others didn't have nearly the personalites or development to make it. I'd like to include Milly, but her graduation was too sudden and is linked to the horrible 12th episode. I don't believe that Kallen and Todoh were "wrecked." Todoh was the same man all of the way. The same for Kallen. She admired Lelouch and saw him as a man who could accomplish what her brother died for, and felt betrayed over his actions. That's a consistent fact. There's no doubt the story pushed her aside a bit, but she wasn't made unlike her season 1 self.
Crusader is full of it. He's right about the Knights of the RounRAB being misused, and that's about it. And what is he doing citing Clausewitz? Implying that Geass somehow fails for having Lelouch win battles through intellect and planning and limited means instead of going for a total-war, scorched-Earth approach? How exactly would his small rebellion have done that? And by the way, wasn't the Damocles pretty much an erabodiment of that principle he supports? How did that work out? This is fantastically absurd. He's essentially mad that Code Geass doesn't happen to reflect his personal belief system. There's no substance there.
Music: It was all good. Some people apparently hate Ali Project. I'm not their biggest fan, but the sentinment strikes me as an overblown fad mostly.
Mecha: I very much agree that in season 1 it was pretty down to Earth, whereas season 2 turned it into an insane tech war. Season 1 certainly had more focus on Lelouch's cunning strategies.
Story: This is ridiculous. You hate the story from an "artistic" standpoint, and yet say you like it? No. Also, I don't give a damn about their assessment of how much Geass contributed to stupid memes and "lulz." Review on the merits period, or go home. The only thing worse than being wrong about the quality of the show is being wrong about the quality of the show and then saying that it doesn't matter because it gave 4chan lots of memes. Sorry if that's harsh, but seriously.
And good lord, Lelouch's survival is not a plot hole. The show was dropping hints about it for a long time. To say that they were "wildly unintentional" is laughable. Do some people just outright ignore Nunally grieving over Lelouch at the end? I really don't understand this. Other elements are surely weak, like Marianne's death. They're right to cite undeveloped plot points but wrong to talk like every twist and turn in the entire show was just a random attempt to shock us. Give me a break. It isn't so just because internet trolls say so. They also don't seem to consider how Lelouch's growth was, in and of itself, an important part of the story.