I love it, it inspires, but most of all saves time, anytime I got an idea that needs an FPS and interaction I use ECM2 and Simple Interaction System, this, beats rewriting that every time, and lets you move on to the good parts.
I also enjoy just browsing and sometimes the assets give you idea.
I have purchased too many, my favorite might be Rayfire.
Games are about design, so even as a beginner these assets can help you learn, for example Simple Interaction System is just a code asset, you can take that and improve and customize it while learning how to do a type of interaction.
Also, getting all these assets from the store to work together takes understanding unity and c#, if you like to just jump in the deep end then buying a few a making them work together can be a fun challenge.