I almost reviewed every Angular Material themes in Envato and I think Gradus is the best.
The source code is really clean and straightforward and even you don't need any documentation if you already know Angular. Everything is in its right place so you can easily change or remove anything you want and you can change general features only by assigning the settings variables whether manually in development time or in your components code.
It also supports RTL correctly. There are many themes that are claimed to support RTL feature but the only thing that they have done is setting the direction to rtl and they did not considered many rtl issues . For example if you have a right-arrow menu icon when you change it to rtl the icon should change to left-arrow. But Gradus on the contrary supports rtl fully and correctly. This is a huge advantage if your app needs to support Arabic,Persian,Hebrew or any other rtl languages.
The online support is good. I had situation in my WebApp that needed to have small rare customization in Angular Material that I couldn't find on Internet and although my question was about Angular Material not the Gradus itself I ask the question from developer and got the right answer in few hours.