For most of the aughts, the various Linux desktop projects tried to catch up to Windows by copying features wholesale, while Mac OS X innovated like crazy and blew past both by building an amazing desktop experience.
The omission of Chrome & Safari from Paul Rouget‘s pro-Firefox Is IE9 a modern browser? reminds me of that misguided attempt. I hope Firefox doesn’t make the same mistake as desktop Linux; it would be a shame if they focused all their energy trying to catch Explorer, while missing the rapid user-interface innovation going on elsewhere.
Update: Here’s an example of a great idea from 2007, from Alex Faaborg, out of the user experience team at Mozilla, that didn’t make it into Firefox 3.