One thing I really like about this game is its accessibility. It's the first 'bullet hell' esque (I say that as it's obviously not true bullet hell) that can be played with a group of relative amateurs, and the game can still be fun, for both them and the person carrying.
In games like Resogun, the less experienced players lose all of their lives and then they have to sit and watch as I clear the stage. On Jamestown, the amateur players die repeatedly due to the difficulty and one-shot death system, and have to sit on a lengthy respawn timer as a result.
In Cactus, single bullets do not kill and they can merely mash trigger to get back up. This doesn't prevent the game being difficult however, it's just relative to your goals on the level. S+ is difficult, clearing stages? Not so much. I like that though, it's good to be able to get a group of friends playing these types of games, and I think it's important for a genre that's otherwise, incredibly inaccessible for newcomers.