If you're creating a preset of your own, you get to choose the animation style and the palette of colors you'd like it to draw from. Playing around with your options and finding the right match for a favorite song is half of the fun.
I do wish that the preset creator went a little further, though. It would be nice, for instance, if you could tie specific colors and effects to specific panels, or designate different colors and effects for bass and treble. Right now, you can't, but I'll be curious to see if any of that changes in the coming year.
The Rhythm module's center triangle doubles as a physical button that lets you quickly switch between presets without taking your phone out of your pocket or relying on voice commands. That's a welcome design touch, especially since voice commands probably aren't the best option when you've got your music cranked up to 11.
At any rate, Nanoleaf Rhythm leans into the same novelty appeal as the Aurora panels it plugs into, so I have to imagine that most Aurora fans will at least find it intriguing. Fifty dollars seems a bit steep as far as single-feature upgrades are concerned, but it isn't outrageous. Most importantly, the Rhythm module works well, is incredibly easy to use and should improve with time. To me, that's the sort of splurge worth spending on.