There's still a market for people who want to manually upgrade. There was a comment thread on HN a few months ago about this as well (no way we'll be able to find it now, I don't remember the story), but it summarized my views very well. I like knowing what is or isn't being installed on my computer. I've got a bash script to automatically download and update to the newest Firefox, so the act of upgrading isn't a chore. But I don't want a given company, be it Google or Mozilla, to arbitrarily change what's on my computer.
That's not to say I don't see the allure of automatic updates, but I just don't want them to be silent and mandatory.
For a web browser there is no reason not to want to use the newest build, especially while HTML5 and CSS3 are being actively implemented. Your bash script is just your own version of Mozilla's auto updater.
Sure there is. A while ago, while I was using the 4.0 beta, I ran into a problem: modal dialogs wouldn't work. In beta 4 they worked just fine. Beta 5, just fine. When beat 6 rolled around, they stopped working. I reverted and used that until beta 12 fixed my problem. 6-11 were useless for some of the things I used it for (example: TiddlyWiki editing) because Javascript alert() and confirm() dialogs would literally not show up.
EDIT: also, the bash script is there because I install Firefox to /usr/local, and it's easier to type "update-firefox" in an already-open terminal than to reboot Firefox as root so it can modify my files. I'm aware it's redundant, but it also a) requires my active participation, so I can't miss it and b) lets me downgrade, in case of something like what happened above.
