You might have heard of it shadow DOM etc. Basically the idea is to be able to add GUI components eg <progressbar> that are as integrated as the native ones are.
Mozilla's X-Tags implementation seems closer to the goal though: http://www.x-tags.org/ IIRC it can do this because it's using Object.observable internally to detect DOM changes.
Unfortunately, we’ll have to stick around with them for the following couple of years, probably, as for now, most of the Web Components APIs are available only in Chrome Canary and Firefox dev builds. Monkey-patching (AKA “shimming”) to the rescue…
In my opinion, the more certain nowadays libs resemble the Web Components specs, the more clear the developers’ choice towards those libs should be.