Finally played this at the weekend - my local arcade has two machines
So, it makes good use of the Konami arcade card, whereby you collect experience to unlock weapons for your custom weapon set. You also unlock different difficulties for each stage, depending how good you are. It seems I pretty much suck though...
The gameplay is basically Gradius, but with a couple of key differences.
1) You don't have lives - you have two shield bars. Your shield energy wears down gradually, and when one bar runs out, you fly off the screen and drop all your power ups. Options stay on the screen and float by, a la Salamander / Gradius V, but all other power ups go. Then repeat.
2) In the sixth slot, instead of shield, there is a "blast" selection. You start with two blasts and you can use them whenever you want to do some whopping damage and give yourself a small bit of invincibility. You can hold up to two at any time, and when you've got those two charged, the blast selection is no longer available. Not sure if this is the same across the board - I stuck to Vic Viper for the two games I played. And there are two ways to use your blasts. One is a single button press to let off a bomb-type explosion. The other is a hold-button-charge-until-ring-is-full thing. After you let it off, you get to touch the screen as much as you want over a period of a few seconds, selecting targets to hit. This could be good, but I used it at a super lame section. The bad part about this type of blast is that you lose all your power-ups, including options. So probably best used as a last resort... unless it's a score orgy type deal. I didn't check.
The first two stages were pretty rocking, but I didn't get any further. I wish arcades let you plug in headphones too... I couldn't tell what the hell the characters were saying and there were no subtitles :/