It's a completely new Dig Dug experience, albeit one that isn't really as fun as the first one.
The core concept is half there: kill every enemy to beat a level. But, instead of tunneling underground to find his enemies, our nameless hero finds himself in a top-down perspective on a multitude of islands. He's still armed with his famous pump, with which he inflates the game's two resident enemies - the round red guy Pooka and the fire-breathing Frygar - to the point of popping. But, the little white guy has some new tricks up his sleeve, namely in the form of a jackhammer.
Each island will have small holes in the ground. By drilling into these holes, he can make splits in the ground in any of four directions. Thus, by making creases that form a circut, entire chunks of the island will break off, taking any enemies, or even Dig Dug, into the drink with it. It's an interesting concept, and sometimes the game will pull a fast one on you and almost send you into the ocean.
Now let me get nitpicky about the controls: you can only move in four directions, which I find to be a handicap of sorts; and as you're inflating enemies, you can't just mash on the A button, as there's about a half-second delay between each "allowed" press of the A button. After playing the first Dig Dug a lot on one of those Namco joysticks, this mechanism makes defeating enemies a lot slower.
Graphically, the game hasn't changed too much. The enemy sprites look the same, although Dig Dug has been updated to suit the game's top-down view. There's also a new soundtrack, which is one song; but it isn't like in the first Dig Dug, where the music only played as you moved. Although this certainly isn't a bad thing.
Several slight gameplay flaws aside, it was a pretty solid buy for two bucks, as opposed to the standard of five I see at my EB.