It does nothing you haven't seen before, but that doesn't stop Bomberman ULTRA from being a lot of fun.
Bomberman 2, however, was a great game. It wasn't that anything changed really, they simply gave fans of the first game a few new levels and powerups, but it added a genuinely entertaining multiplayer mode. That same dynamic of a mediocre single player game with a fun, addictive multiplayer mode would continue through most of the following games in the series. Sure, you would occasionally get Bomberman 64 (or Baku Bomberman as it was called in Japan, the Japanese Bomberman 64 was as traditional as can be) or Bomberman Hero, two N64 games that flirted with more exploratory gameplay, but for the most part Hudson kept Bomberman untouched through its dozens of releases.
Bomberman ULTRA is essentially the Xbox Live Arcade Bomberman Live! with all of the downloadable content already installed (and free of course). ULTRA completely eliminates the single player game (save for bot options), putting the focus squarely on online or offline multiplayer battles.
The multiplayer is essentially identical to the single player campaigns of old, save for the fact that you are fighting intelligent humans rather than mindless droids. What really makes things chaotic is that any bomb hit by a blast goes off immediately, that includes ones you haven't set yourself. Everyone starts off separate from one another, each inhabiting a position on the grid that is either fixed or randomized, as per the host's settings and then need to blast through destructible blocks (indestructible blocks are usually arranged every other space in every other row) to open up paths to other players, in these blocks is the occasional powerup. That's it, it's simple in concept, but ludicrously entertaining and addictive.
By collecting costume balls you can customize your character, but its only superficial and for some reason only appear in local matches. It does nothing you haven't seen before, but that doesn't stop Bomberman ULTRA from being a lot of fun.