I don't know of anything that is completely broken, but some functionality requiers chrome:
On Google Docs, paste as markdown, copy and paste from menus, paste without formatting, etc. only works on chrome. This functionality could be done with standard APIs, but instead google uses a hidden, pre-installed extension to implement it.
Offline mode doesn't work on firefox for either gmail or google docs.
Google doodles don't show up on Firefox Mobile, unless you spoof a chrome user agent.
Youtube has repeatedly had serious performance problems on Firefox.
On Google Docs, paste as markdown, copy and paste from menus, paste without formatting, etc. only works on chrome. This functionality could be done with standard APIs, but instead google uses a hidden, pre-installed extension to implement it.
Offline mode doesn't work on firefox for either gmail or google docs.
Google doodles don't show up on Firefox Mobile, unless you spoof a chrome user agent.
Youtube has repeatedly had serious performance problems on Firefox.