...is amazing. I just played for three hours with hardly a break. If you like Metroid-style action games, this is the best 1000 Wii Points you can spend. Overdrive is NOT a remake of Blaster Master; it is an all new sequel. It keeps the essence of gameplay, in both tank and overhead sequences, but all the content is new. New maps, new enemies, new upgrades, new weapons. There are also some much appreciated modern features, like save points and an auto-map straight out of Super Metroid.
The tank sequences feel exactly like those in the original Blaster Master, in terms of physics and layout. The main difference is that your weapons and hover are now limited only by an energy meter that automatically refills after a few seconds. Gone are the consumable sub-weapons and deviously rare hover packs. Hover can no longer get you higher than a regular jump, but that's where the grapple hook comes in. That's right, Overdrive combines my two favorite game mechanics of all time, flying and grappling, with a Metroid-style world full of exploration rewards. There are health and energy upgrades all over the map, some requiring a lot of skill to reach, not to mention the right tank abilities.
The overhead sequences, while intact, barely resemble those in the original game. That's a good thing! You can now shoot in eight directions, and holding the B button (under the Remote... not entirely comfortable) lets you strafe at the cost of some walking speed. You have three different weapons available from the very start of the game. There's the standard gun, a weaker homing weapon, and the powerful but slow grenade launcher. All three can be upgraded separately up to level 5, with each level bringing faster and more powerful shots that even look cooler. You still lose a weapon level when hit, so it pays to be careful and dodge enemy shots. This classic element makes boss fights particularly tense, as the more you get hit, the more difficult it is to win.
While Overdrive is still challenging overall, it is nowhere near as hard as the first Blaster Master. Enemies frequently drop health pick-ups, and with the save system, dying is not a severe punishment. It's also easier to find your way around each area, thanks to the auto-map. Most of the overhead areas contain at least one permanent health upgrade in addition to weapon pick-ups, so it's worth exploring every cave. (The original game had many dead-ends and practically worthless, yet dangerous, overhead caves.)
I should also note that the graphics are fantastic, and the music is quite good. Each area has a different song, and while some are better than others, they all sound better than that remix you heard in the trailer.
[Edit: fixed the game's subtitle... thanks, Neal!]