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.
The soundtrack of the iPhone version was composed by Ken'ichi Maeyamada, also known as Hyadain, and therefore contains a lot of awesome tracks. However, special mentioning deserves the True Final Boss theme "Battle for the Last", which also has a vocal version sung by Hyadain himself, as usual.
Fridge Horror — The Fan Nickname for DaiFukkatsu Black Label's 360-exclusive Arrange Mode, a crossover of DaiFukkatsu and Ketsui, is "Ketsupachi". "Ketsu" in Japanese can mean "buttocks". So "Ketsupachi" means "Ass Bee".
Nerf + Dynamic Difficulty — In DaiFuukatsu BLACK Label, playing in Strong Style is often likened to playing on DFK 1.5's second loop. One player commented that "it feels like the enemies are in strong style, not the player."
Also in DaiFukkatsu, Bomb Style and Strong Style's auto-bomb mechanic. If you get hit with at least one bomb in stock, you use a bomb instead of dying. It does last shorter and does less damage than a manually-fired bomb, but that you can use your bombs as extra lives is still pretty broken. Moreover, on each successive life, you start off with one more bomb than your last life can hold, so by the time you're on your last life, you're carrying 6 bombs, or rather, 6 extra lives. The BLACK Label version allows you to turn it off, and Version 1.51 Nerfs auto-bomb by taking away all of your bombs if you auto-bomb instead of manually bombing.
Do note, however, that if you are playing for score, and unless you are playing Version 1.51 or either of 1.5's Arrange modes, bombs wipe out your combo (alongside getting killed), and thus subvert this trope. A single touch of another bullet will destroy that 15,000 combo of yours whether you die or not.
Older Than They Think: DoDonPachi Campaign Version features a prototype version of the Hyper mechanic. It also introduced the idea of having the value of bee items being multiplied by your current combo. In a way, it is a prototype DaiOuJou, especially considering its extreme difficulty. This version was presented to the winner of a scoring contest that happened in late 1997 to celebrate the release of the Saturn port; this was approximately 4.5 years before DOJ was released.
Porting Disaster — The Xbox 360 port of DaiOuJou is not just glitchy, it nearly caused legal trouble! A patch came out that resolved some of the glitches...two years after the port's release...after it went out of print. Thanks 5pb, you assholes!
Scrappy Mechanic — Using Leinyan's laser bomb in DaiOuJou Death Label will heal the boss, but Shotia's and Exy's laser bombs won't (at least until stage 4). Wait, WHAT?!
Sequel Displacement — DoDonPachi is far better remembered than DonPachi, mainly due to DoDonPachi taking DP's bullet patterns and action and cranking them Up to Eleven.
Sequelitis — DoDonPachi II is one of the less well-received installments. It didn't help that it was developed not by Cave, but by IGS, a lesser-known Taiwanese development team.
Surprisingly Improved Sequel — DonPachi was mainly notable for being hard but fair, for its second loop with suicide bullets, and for a few interesting game mechanics. It was otherwise not very interesting in the grand scheme of things. Then DoDonPachi changed the 2-D shooter world forever.