MAJOR SPOILER ALERT FOR ANYONE WHO HAS NOT SEEN THE FINALE YET:

I LOVED THE FINALE! I'm perfectly satisfied with the ending to the series as a whole. 
I adored when Spike became 2nd in command to Twilight as "Royal Advisor." Spike SO deserves a high position and a proper title! It was so touching when Celestia and Luna spoke about being "all grown up" on her throne. How far Twilight Sparkle has come in 9 seasons….Her interest in magic started with the summer sun celebration so she has truly come full circle.  I was shocked and completely surprised that Discord turned out to be Grogar all along. I really like this twist as it explains why Discord was absent from the MLP 2017 movie for example. It was perfectly in character for Discord as he has to be chaotic to help or he disappears completely from existence. It was interesting to see how Twilight reacted to Discord's manipulation of their past victories. I'm glad the writers got to explore this with Twilight. 
The battles were wonderfully animated. Twilight gets injured! I never thought the writers would take the risk of having a member of the Mane 6, least of all Twilight, take a hit even though Discord and Celestia have been injured in past episodes(albeit Discord faked his injury). This was one tense episode! Also Cozy turned herself into an Alicorn! I would have expected a bit more of a reaction out of the friends when Twilight gets blasted by Cozy…that has got to be permanently scarring for Mane 5. 
I loved that every creature/character came to rescue the Mane 6 in a true moment of friendship, diversity and inclusion done right. Before I ever knew that season 9 would be the last season, I wanted the finale of MLP to have a moment where all of Equestria saved the Mane 6 because that would be the perfect way to show unity and the strength of friendship so I was thrilled that the writers felt the same way. I liked that the Windigos got to make a return when the ponies became divided. I never liked the idea of the pony races being racist towards each other because it always felt unnatural to me in the MLP universe but here it actually works well and gives the Student 6 a minor but vital rule in the conclusion of the series. Sorry I just love the final friendship rainbow scene! Ultimate Friendship Beam anyone?! I love how Spike is included for once! Tempest makes a non speaking cameo! Pinkie Pie using Discord's magic from the bell was hilarious because she seems so chaotic in a way herself. 
I love the concept of the finale episode "The Last Problem" to pieces where we get to see what became of everyone without squeezing it into the battle episodes(Pinkie’s a mom!)!. I loved that we got to see characters like the Cake Twins and the CMC older! The lesson is perfect! It’s still weird that Twilight can’t rule from Ponyvile in her own castle though. It doesn’t make sense why Twilight can’t just rule from Ponyvile since she already has a whole castle there, and why she can’t continue to teach in Ponyvile. And I wish it was explained whether the other Mane 5 will teach at the friendship school, at all after Twilight takes power, or do they have other duties, royal or otherwise?? Does Sunburst have to live in Ponyvile now? So many unanswered details.  I love Twilight’s coronation outfit! I love how Celestia and Luna combined their crowns to make Twilight's big new crown. The song was utterly beautiful! The last moment with the closing of the book was the perfect touch. I love how the TV airing had "Many, Many, Many Moons later" on the title card before "Last Problem" actually started. I loved the disability representation of Scootaloo still being flightless and being fully respected as a disabled teacher at the School of Friendship! 

Please NOTE: NO I do NOT think Twilight is immortal and no I do NOT think Twilight will outlive her friends and neither does my family who watched with me. This is more of a fan theory but I think Alicorns do age, but don't show their age physically because of Alicorn magic. I think Celestia and Luna were elderly and getting weaker, hence why they didn't go on adventures much and decided to hand over ruling duties to Twilight and her friends, especially since Celestia and Luna mentioned the "Sliver" retirement community from the previous episode "Point Of No Return" and all the ponies at that location are over a certain age, if you will.  

Goodbye MLP. I will treasure my time in Equestria with all these characters forever. Thank you MLP staff for making a show so good it inspired my own film writing style. Can't wait for G5 and the CGI movie and the MLP comic series.