That is exactly how I use it and it works great for that.

Among other things, I love that I can subscribe to RSS feeds and then save individual items I want to be able to reference later on.

Before that I tried several things, local bookmarks, bookmark services (actually just delicious), and an org file for references, but Zotero is the most seamless system for knowledge repository for my use case.

If it can save web pages, it will solve most of my electronic life problems.

I doubt it can (otherwise everybody would be using it as a personal knowledge management solution, I assume). I'll take a look anyways.

It can!

Mostly just PDFs? Or are there good ways to save non-PDF content?

The web plugin actually falls back to 'web page with snapshot' if it can't detect a journal paper, which in many ways is better than trying to drag around big PDF binaries.

Thanks! I've used zotero only minimally, mostly to support users of my software who use zotero, rather than using it myself for my own purposes.

Is the "web plugin" something built into zotero, or an extra plugin to install? Calling it "plugin" makes it sound like something extra to install, but not finding it easily googling. Help me out?

I think OP talks about the Zotero Connector Browser Plugin. So its not a plugin for zotero but your browser (Firefox, Chrome, Safari and Edge are supported) The plugin ads a button to the Browser where you can add the currently viewed page to your database. It even tries to detect references to papers or other content and choose the matching entry type. Eg on Google Scholar you can choose which search result you want to add. It its a PDF the file gets saved to your zotero database.

All in all very handy.

Does it also save the JavaScript and images, so that the page can be "archived" locally?

You can link to any type of file and it will open in the default program for that filetype when you double click