Bonk, er Zonk, made the transition to Shmup very nicely.
First of, it has five very colorful levels. Some of them are quite trippy. You fly around as Zonk, who, by the way, has the largest head I've ever seen. You can pick up power-ups and each one has their unique flair. You can also charge your shot up to a screen clearing bomb. In addition, there are 10 helpers that act like options for you, meaning they lend their specific firepower to the foray. Pick up the helper option a second time and you go buck wild and merge with your helper into a hybrid beast with plenty of firepower. You also get like 15 seconds of invincibility to boot. But, that doesn't mean the game is a cakewalk. I'll admit, the first two levels are easy, but things ramp up in the third and fourth only to get to near impossible in the fifth. By the time you beat the four first bosses a second time in stage five, you'll be screaming for mercy. Only thing is, that the level isn't even over yet, ultimately leading to one extremely tough fight with King Drool. Luckily, he'll give you 9 lives, but even then you'll be in for quite a challenge. Good thing the game grants you three difficulty levels to appease players of all skill levels.
Now, for the bad. The levels are fairly short. The exception is the last level, which seems to drone on forever. There are no level checkpoints. When you lose your last life, you have to continue at the beginning of the level. This isn't so bad for the first four levels, but that ultra huge last level is a royal pain in the arse. That even includes if you die at King Drool. I swear, it takes over 10 minutes to play this level alone. That's like over a third of the game right there, no joke. So it get's a little frustrating to say the least and it detracts from an otherwise enjoyable game.
Bottom line: If you have 600 Wii points, you can't go wrong with this shmup. It may not have the depth, sounds or colors of say a Gates of Thunder, but it's quite good. An extremely frustrating final level might put off some, but you can't say it isn't challenging.