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 is kept synchronized between PCs, and the centralized web-app arrangement makes more efficient use of network resources. Better to have Google Reader poll a site every 30 minutes than to have 10,000 Firefox installs each polling it every few hours.
The only browsers I know of that ever had good in-browser RSS readers were Opera and Seamonkey. But even in those cases, RSS was included as part of the mail client, not shoehorned into the browsing paradigm.
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.
I've always used the browser RSS button precisely in order to add feeds to Google Reader -- I feel like that's the button's main use case. It's an immediate, standard way to see whether a page offers a feed, and to quickly save the feed in your reader. I've found it incredibly useful.
It's been a while since I used Firefox's RSS button. I see it offers more options than I remember (like subscribing with a web-based reader). And it looks like the plan is to eliminate any standard in-browser indication of the presence of an RSS feed, something I didn't really catch from the blog post's talk about a "button on the toolbar."
That does seem pretty inconvenient. Many of the posts at bugzilla argue that the most important feature of the button is the fact that it indicates, in a standard way, that feeds were detected. And I agree.
On the other hand, since it's Firefox, there will probably be several feed-finder extensions available before 4.0 is final.
> A full-featured RSS reader feels a lot like a mailing list
Yep. I read all my RSS feeds in my mail client, claws mail. The feeds display on screen just like a mailing list. Plus you get the benefit that most email clients have such as deep searches, filtering, etc.
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 is kept synchronized between PCs, and the centralized web-app arrangement makes more efficient use of network resources. Better to have Google Reader poll a site every 30 minutes than to have 10,000 Firefox installs each polling it every few hours.
The only browsers I know of that ever had good in-browser RSS readers were Opera and Seamonkey. But even in those cases, RSS was included as part of the mail client, not shoehorned into the browsing paradigm.