I still remember getting the lite version of the original DU (about a month before the full game was released), and absolutely enjoyed the stuffing out of it. Then the full version was released, and I couldn't have been happier. Until DU2 was released and a whole new game mode was introduced and the touch controls were tweaked and changed and felt flawless. The upgrade system was great, and trying to find the setup that I best worked with was great fun. Both games are still on my phone today. And now there's the third.
And just like DU2 was quite the step up from the original, DU3 is another step up from the already basically flawless DU2. Graphically, the game is beautiful, and the controls are spot-on (with the option to change the relative touch to movement ratio anywhere from 1:1 to 2:1). The music is done by Blankfield (who did the OST for Storm Strikers and DU2), and is top notch... and the weapon/beam unlocking is done by reaching goals or getting achivements (complete the game on any difficulty, graze a total of 100,000 bullets, reach a score of 1 billion, ect...). Right now, I've only played on Easy and Medium difficulties, but the bullet patterns and enemy placement/timing all works together so incredibly well. It's absolutely crazy to think that this was made by ONE PERSON.
I still consider DU2 one of my favorite titles within the genre, and I'm very confident DU3 will find itself on that list very soon as well. I can't recommend it enough.