This is a short review, 'cause I want to get back to playing it, but let's get to the pretty bits right away:
The game runs very smoothly indeed. Cave's learned a lot from Espgaluda, and starting a game has about five fewer menu screens as most options are set, weirdly enough, in the options so you don't choose them every time. Once playing, the game is relentlessly great.
The game features two main modes, Arcade and Iphone. The former's just like the arcade, with a chaining multiplier that increases with each enemy killed, but resets if you wait too long between kills. This means you're constantly on the lookout for slow patches, and dragging out kills or rushing to destroy something before the counter (and your score) drops.
Iphone mode features a very cool gimmick: the S & M gauge. When you destroy an enemy, the gauge shifts towards Slaughter, and when you scrape close to a bullet (or more often a stream of bullets) it shifts towards Menace. When you're in slaughter mode your multiplier is constantly dropping, so while annihilating fields of popcorn enemies bumps it up, any slowdown in the frenzy sees it steadily decline. In Menace mode the multiplier doesn't decline, so you're faced with an insane requirement: stay close to the enemy's bullets to maintain your multiplier. Play it safe and your gauge starts to shift towards S, and when it crosses the central line, your multiplier starts dropping very quickly.
Maxing your multiplier at 1000 and acing a level and its boss is very rewarding. =D
And now, please, let me mention the music.
The music is awesome, the very best shooter music since Raiden DX, and that's saying something. It's catchy, it's fun, it's a little bit frantic, and while playing it last night I was wiggling my feet.
I want the soundtrack and I want it now.
It's $4.99 ($5.99 AUD) for a limited time. It's worth twice that price, but get it while it's cheap and live extra happy!