Some more notes:
One important thing to notice is that currently the path to the icons in manifest.webapp MUST begin with leading slash, event if the icons are in the root directory.
I still cannot wrap my head around the styles and the layout on buildingfirefoxos.com that's why the app looks quite ugly and non-native.
IARC - that's new to me. Looks like three moths to get certified and to do that, one have to answer some questions about what the app contain and do.
This app will be disabled if no content ratings are assigned by April 15, 2014: Set up Content RatingsActually the process took me 5 minutes on slow connection so it's not a big issue.