Like Instapaper and Pocket (was Read It Later), Readlists lets you save links to content you want to read at a later date.
Like Instapaper, DotEpub, and GrabMyBooks, this tool will also let you convert the content to Kindle or Epub files. (Those latter 2 tools are bookmarklets which do immediate conversions of whatever you're looking at.) It even lets you strip out the extraneous ads and formatting.
But one thing that sets Readlist apart is that it can pull together multiple sources into one Epub. This can be useful if you're building a briefing doc of some kind.
You can also easily share the ebooks you've made, and that could be one of its breakout features. That sharing ability might turn Readlists into a new type of blogging tool, or at the very least a new way to share content.
As for me, I probably won't use ReadLists. In fact, I don't use any of the tools mentioned above.
My current method for saving content for later is to tweet a link. This give me both a readily accessible link as well as allowing me to share it. Now, I don't save but a fraction of what I read, and if I did save everything then tweeting the links would clutter up my timeline. But right now it works for me.