Definitely the best music player around for big libraries. I'm at over 250gb of lossy audio (about 30k files) myself and experience little to no lag when navigating the browsers and art grid. The customizability has allowed me to arrange the interface exactly to my liking. The overall lack of fluff while still having a fantastic interface is a godsend. It's minimalist, but not in a lazy way. Aside from a couple issues I've had, Swinsian makes other Mac OS music players look like a joke.
Changing the grid's icon size is an exception to the lag-free experience and is especially frustrating because it's extremely easy to mess everything up with an accidental zoom gesture and go through the laggy, frustrating process of getting it to the right size again and again. A simple "lock" button next to the size slider would completely fix the issue.
More importantly, if the developers are reading this, please PLEASE implement a dark mode soon. Among the many different applications I have running on a regular basis, this has been only one that has yet to give my eyes a rest even among a bunch of other third-party developers. I paid full price for this software and am disappointed that such a simple yet important feature is still nowhere to be seen.