When I open Firefox and visit any of the webapp enabled webpages I have installed, I get a launcher icon for them. The same does not appear to be when I use for example Google Chrome. Do webapps only work for Firefox?
The new webapps feature only work with Firefox and Chromium. Google Chrome is not supported because it doesn't allow adding new extensions outside of the Chrome web store while Firefox and Chromium are both open source browsers and adding a new extension isn't as difficult.
That said, if someone does the necessary work to get it integrated into Google Chrome, it might work as well. I just don't see it happening for the 12.10 release.
If you search for the chromium browser in the Ubuntu Software Center these are available as technical items (click on the "Show number technical items" link on the bottom of the search page).