Well, I don't know about flawless... Though much like Magical Mystery Cure, I consider this two-parter to be as close to flawless as possible, with a few minor nitpicks on hand. I still have a hard time buying that Tirek had a.) been wandering around Equestria since It's About Time yet b.) did NOT know about Discord's freedom or Twilight's ascension to princesshood. It's a bit of a stretch, though I'll grant that it's not truly a flaw. I'm also having a hard time wondering why Celestia told Twilight not to tell her friends about her newly acquired alicorn powers, plus the fact that the alicorn magic here doesn't at all look like the alicorn magic Twilight used in Princess Twilight Sparkle. Also, Tirek had the chance to drain Twilight's power during their fight, but instead just threw her into a mountain... eh, maybe he was caught up in the excitement of the fight. I also found the songs underwhelming, NOT BAD, just not all that memorable. And the fight scene, while epic beyond belief, just left me wondering... this is still a little girls show, right? I mean, not that all little girls shows need to be about tea parties and dressing up, but... would little girls really be into this kind of thing? Also, apparently, Twilight was going to actually PUNCH Tirek, but that got rejected...
This kind of ties into the question of where to go from here. This season has been VERY out there, and I've seen people turned off by it to the point of not watching the series anymore. I'll admit, while this is undoubtably my favorite season, it did seem very... gimmicky, and went a bit too crazy here and there (I guess that's to be expcted when you have the Queen of crazy writing, Meghan McCarthy, running the show). Not to mention, with the season finale having blown many away, people will likely be expecting the series to get even bigger somehow from here, yet if Meghan McCarthy and the staff try to do so, they'll end up in Power Creep territory long before you know it, and the amount of effort they'll have to use to make bad guys even more threatening then Tirek will be staggering to borderline ridiculous. I sincerely hope they don't fall into this trap and reel it back for season 5.
...All that out of the way, I completely agree, this two-parter was amazing, 5 stars, ten out of ten, just fantastic! The negativity towards this episode... eh, I try not to let it get to me. After all, I can be really negative about a lot of things, and it really bothers me when people claim that I'm just being negative for negative's sake, when really that's just how my mind works, and these things really DO bother me. I think it speaks to how good some things are when things don't bother me as much, hence why they're great.
I was under the impression that the whole "Twilight's tree" thing was a joke and always was meant to be a joke, and I didn't think ANYONE took that seriously or was THAT genuinely upset by the tree's destruction. It was hard for me to watch Fluttershy's heart being broken, though, doubly so when Discord was betrayed, so now he knows how it feels.
I just want to say, the exchange between Discord and Tirek when they initially meet in this two-parter is probably my favorite part of the whole thing. I LOVE the dialogue, and I love how tempting Tirek can be, it's all so convincing and very well done!
Also, how exactly did they defeat Tirek before? They apparently defeated him without Discord's help, at least that's what it sounded like from the backstory. Not that it matters, since Discord has allied himself with Tirek, and since only the Elements of Harmony could defeat him, they're out of options.
"The point is to stay hidden, dipshit." Well I find that rather rude. After all, Twilight's friends aren't about to tell Tirek where the alicorn magic or Twilight is. That also doesn't explain why Twilight didn't tell them about Discord's betrayal, so they'd be prepared... Then again, maybe Fluttershy would trust Discord too much and let him know. Still, I don't think it's AS obvious as you made it out to be, though I understand your bluntness, given how frustrated you are.
Also, I prefer not to believe that this is a plan from Discord to open the box, because if it was, it would remove the genuine emotion he had when he felt betrayed by Tirek and humbled by Twilight. I prefer to think that Discord didn't tell Tirek because, like he said, he wanted to make sure their plan was a team effort, and thus kept this information as a means to get out of it should it seem like Tirek would betray him.
I agree with you on the whole "try to find something nice to say" deal, as well as the whole "I don't enjoy failing/critiquing an episode". You know what I find especially ironic... I distinctly remember DigiBro admitting he liked saying negative things about an episode because he got to say what he thought about it and write it out and talk to others about it. I feel like that's a wrong-headed mindset to have, and that might be why he suffered quite a bit of backlash this season.