This game feels like a road trip. I guess it's a road trip where you shoot monsters while in the car, and then make pitstops to shoot more monsters. There are parts that can feel slow, but they also feel like times to just enjoy the scenery. I think the aspects of this game that bothered me would bother me much more if I didn't know it has two sequels, which to my understanding greatly remedy these flaws.

Addendum: Destroyer mode is an interesting alternate mode for those who thought the main game was too easy. Very trivial tasks like traversing a single screen can become serious challenges. Having to rely on your entire available arsenal to clear the game makes it a lot more fun, in my opinion. Still retains some of the same frustrating features though.