Awesome Music: A number of the themes used in the series are quite catchy, including (but not even remotely limited to):
Vivio's transformation theme, sharing her perkiness and upbeat attitude.
Einhart's transformation theme. Its sense of mystery and seriousness fit the Hegemon perfectly.
The mock battle transformation theme. A perfect track to get pumped up for a fun battle.
The track that plays during Miura and Micaiah's match as well as Corona and Einhart's match when the latter begins their late-game counterattack. The beat and the deep, powerful guitar give the scenes the sense of determination they showcase.
An early popularity poll, when only a few of the Inter-Middle participants were just introduced, has following characters in the top 10. Tenth is Erio, ninth is Corona, eighth is Caro, seventh is Lutecia, sixth is Nove, fifth is Rio, fourth is Einhart, third is Nanoha, second is Fate, and first is Vivio. It's impressive to see that Nanoha and Fate were still that popular (well, they are the original heroines), but more impressive are Lutecia, Erio and Caro, who are above Subaru and Teana.
This poll was started at the time, when the Takamachi family, Team Nakajima and the Forwards visited the Alpine family in Carnaaji.
The latest poll has also some surprising darkhorses among the Top 20. While it is not surprising that Team Nakajima are in the Top 10note Vivio is 1st, Einhart is 2nd, Corona is 5th and Rio is 6th, the other ViVid characters have Sieglinde, Harry and Fabia at place 8th, 9th and 10th, respectively. Micaiah is 12th, Olivie is 16th, Chantez is 17th and Victoria is 18th. However, the surprising darkhorses are listed below.
The three Aces are also in the Top 10, with Nanoha being 3rd, Fate being 4th and Hayate being 7th. This is surprising, since the fanbase seem to love Fate and Hayate more than Nanoha, yet Nanoha is ranked higher than them.
Three of the Numbers also made it in the Top 20. Nove is 14th, Cinque is 19th and Sein is 20th. Another StrikerS character who made it is Lutecia who is 15th.
Ixpellia reached the 11th place.
Fan-Preferred Couple: Not too surprising considering the similarities between Nanoha and Fate but Vivio and Einhart is now one of the most common and popular pairings in the franchise besides the aforementioned two.
Hilarious in Hindsight: In the end of chapter 35, the translator makes a gag by letting Miura saying "It's my manga now, bitch!", after she defeated Vivio in the tournament. In Magical Girl Lyrical Nanoha The Movie 2nd A's Tribute Comic, all major competitors but Sieglinde and Fabia are cosplaying The Movie 2nd cast. They are later divided in the Mid-Childan and Belkan teams, with Vivio opposing the three other members of Team Nakajima, Miura and Harry. One could say, Miura is stealing her friends, too.
Moe: Nanoha always had a strong element of moe (before Force anyway), but ViVid really pushed it to new heights with characters making cutesy poses and winking at you every other page. Even twenty-something Nanoha and Fate are no exception. Looking only at the magazine posters and the artbooks you'll never guess it's a Fighting Series, and not some kind of ecchi manga revolving around cosplaying, hot springs, beaches, and generally dressing little girls as inappropriately as possible.
Tear Jerker: Even knowing that it was a Foregone Conclusion, Chapter 55 is this. Olivie becomes Saint King of the Cradle, forfeiting her life to end the wars, Claus dies on the battlefield shortly before the war came to an end, forever feeling powerless for failing to stop Olivie, and Jeremiah is placed under house arrest for ten years, never seeing either of them ever again. The panel of Olivie crying as she departs from Claus after their last fight pretty much encapsulates the emotions in this chapter.
The Scrappy: The latest poll hints that Miura seems not to be very popular, despite being basically the fifth main character is prominently featured in artworks and she even makes it in The Movie 2nd A's drama CD and DVD Commentary. However, she is not included in the Top 20. This is most likely due to the fact that not only does she defeat Vivio, she defeats Vivio so early in the Tournament Arc, she doesn't get a chance to deal with anyone else. Though this may be a case of Americans Hate Tingle, as she seems to have more popularity among the Western Fanbase for these same reasons.
Crosses over with Creator's Pet at points. Not only is Miura heavily featured in marketing and commentary, she's also The Ace of the newcomers, a Lightning Bruiser without any ancestral connections, who still defeats Vivio and not one but two veteran finalists. And just to top it all off ViVid Strike! reveals that she is ranked 5th in the U-15 world rankings, two spots above Vivio meaning that a year later and she is still stronger then Vivio. That said, Vivid Strike also gives one hell of a Take That, Scrappy! moment with Rinne brutally defeating and breaking her ribs and it being Vivio who hands Rinne her first on-screen defeat.
Also, it's mentioned at one point that the reason Vivio lacks many of the abilities she displayed in Magical Girl Lyrical Nanoha StrikerS is because her Linker Core was damaged during the battle in the Saint's Cradle. This could have been an interesting character exploration if we'd gotten to see Nanoha's reaction to having effectively magically maimed her daughter, but instead it serves solely as a blatant excuse to nerf Vivio so that she doesn't curb-stomp the other girls in the tournament arc.
Vivio does manage to regain her Sankt Kaiser form after training under Nanoha and is shown to be able to curb-stomp Einhart as hard as Sieg did, but after careful inspection it's really only an aesthetic change to signal that Vivio has started to fight like a Glass Cannon who puts herself in even more danger compared to her usual counter-hitting fighting style. This does signify that Vivio now has better control of her mana, but it still doesn't say anything about Vivio's Linker Core specifically.