Server Push provides significant performance gains if used judiciously. However other WordPress plugins that handle server push can actually slow your site as they push files indiscrimentally.
Most push all files enqueued by wordpress to the broswer and use output buffering to achieve this.
However this plugin does it properly by only pushing the the assets that the browser requires for the initial user interaction. Namely the scripts and css in the head of the document.
Note : It requires a web server that supports HTTP/2.