These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Americans Hate Reflec Beat: Amongst the English-speaking BEMANI community, Reflec Beat was historically not very well-received compared to other BEMANI games. As of 2014, this has been less of the case, with more American fans playing it.
Goddamned Bats: TOP notes. They're hit at a different height from regular notes, making them particularly annoying for beginners. It's not uncommon to get confused by seeing a fading note when it hasn't even hit the timing line yet, only to realize a moment later that it was a TOP note that you just missed. While many charts can still be cleared without hitting TOP notes, you will most likely lose to your opponent from missing notes (especially Just Reflec notes, which carry an extra penalty for missing), and some charts, particularly Shakunetsu Beach Side Bunny on Hard, have enough TOP notes that ignoring them guarantees that you will fail.
Ho Yay: For some reason, the series is the origin for a number of songs with gay subtext:
Juicy, a romantic tune sung by DJ YOSHITAKA (and, in the full version, kors k as well). The artist is credited as "kors k Lovers DJ Yoshitaka".
VENUS, a unit consisting of Sota Fujimori composing the song and Yoshitaka on vocals, has brought us "Survival Games", "Far Away", and "Wow Wow VENUS", all of which have the duo posing in not-so-innocent ways on the songs' respective album jackets. The last one is particularly infamous amongst English speakers; "Wow Wow VENUS", a line repeated throughout the song, can be easily misheard as "Wow Wow PENIS" (to say nothing of the question of what Yoshitaka's looking down at on the jacket...)
BONUS is like VENUS, but with kors k instead of Yoshitaka. Their sole non-cover song so far is "Going My Way".
Limelight had "HAERETICUS" and "量子の海のリントヴルム", both of them pretty douchey in their own way.
It's easier to just list them off when it comes to later games: "Valanga", "STULTI", "ZZ", "chaplet", "Elemental Creation", "Zirkfied", "海神", "Lisa-RICCIA", "IX", "CLAMARE", "onslaught". The last one is written by PHQUASE, who wrote the chart for "Max Burning!!", and most definitely hates you.