FF4 did not remove the Feed icon entirely, it's been removed from the awesome bar, and defaulted to off, but it exists as a positionable toolbar icon, you just have to configure your toolbar, and add the icon whereever you want to regain access to it. My recommendation for the position is the very right end of the awesome bar, for familiarity's sake.
Thanks a bunch for pointing this out. I was annoyed they removed it but not yet to the point of searching for it (although I did hope for a comment like yours when coming).
