I'm just really satisfied with this game. It feels like ZUN's let himself improvise and made something odd and new and shiny in the process, you know. I don't think this'll be like a start of a new wave of gameplay, but we'll look back at this and find it has a special place in the Touhou series.
The soundtrack goes well with the attacks and enhances the mood, it's a good showcase of his new chrome-plated sound.
The attacks themselves I could write an essay on. As a game designer, I find them interesting because they shed new light on how ZUN thinks about things. In the main games you have unwritten design rules about what sort of bullshit can be thrown at the screen, imposed by how the player is expected to pass a series of attacks with limited lives. Here, it's all out of the window - you're allowed to have surprises, impassable walls, wide ranges of movement, excessive amounts of stuff piling up in the game board. But it's all focused on the items, so these cards are built on the idea that there's more than one way to do things. You have to be able to evaluate when you can simply dodge and when's a good time to use an item instead. Trying out combinations and figuring out strategies for each adds a puzzle aspect that'll surely keep completionists entertained.