The implementation of RSS in Firefox was always an "ultra-lite" version that I doubt will be missed by any serious RSS enthusiasts. A full-featured RSS reader feels a lot like a mailing list, so I think it's appropriate to keep RSS in Thunderbird rather than Firefox. In some respects, a web-app RSS reader (like Bloglines or Google Reader) is better. You can access your feeds from any computer, the read/unread status…
I once wrote a Python script that would parse RSS feeds and write emails in a maildir (or whatever is supported by Python); one was then able to read news from an MUA which was comfortable (Mutt by then). I lost that script when I did a 'dd if=/dev/zero of=/dev/sda' before quitting my last job and realizing 2 minutes later that I forgot to backup many useful scripts I wrote over the course of my year and half in that NGO.
Being a smoking Frenchman, I'm tempted to be gratuitously insulting to the author but there's one interesting problem that could come from RSS' disappearance from browsers: the lack of visibility may very well "destroy" the format in the long term. Also, as the web is increasingly publicized, the incentive to remove a format that generates traffic but may hardly generate revenue might be high.