I'm enjoying Opera 11 quite a bit. I'll most likely only use FF 4 as a backup for contrary websites that don't play nice with Opera (which are getting fewer as the years go by).
Aye, I do the same (though I've yet to update my Firefox to FF4, I only installed it at work to check for any breaks with extensions we use and/or important websites before deploying it office-wide)
I wish, though, that Google would stop artificially holding back Opera. Every new feature Google's added to their services work flawelessly in Opera, but they don't have them enabled for Opera (so you gotta change your user agent string to get them)
I don't.
I'm using an outdated version of eeebuntu that refuses to update. I'm also terrified of updating firefox lest flashplayer stops working. Took me hours to get that.
Tarballs are distro-agnostic, so you'll find them for most Linux software. Firefox doesn't do binary packages, instead just a tarball. Since you're using a *buntu, your best bet is to look for a Firefox 4 PPA, there's always a few Mozilla PPAs out there
Edit: https://launchpad.net/~mozillateam/+archive/firefox-stable (assuming your *buntu is at least not so outdated as to be based on 9.10 or earlier)
Edit2: Honestly, it sounds like you need to get rid of that distro and get something more modern on there.