I'm using Firefox 3 beta 2 right now, and find it's not only slightly faster than Firefox 2, but in my case only using half the memory. And I have 13 extensions on it.
The thing of it is, Epiphany is fine, but without extensions like AdBlockPlus, DownloaderHelper, and CustomizeGoogle, it's pretty much useless to me. Opera has loads of widgets, sure, but a lot of them are frankly useless - just how many Chuck Norris facts do you need? Is flipping text upside down really as essential as ad-blocking?
If you're running KDE, Konquerer is fine. You can use Konqueror in Gnome, too, I've been told, but it requires downloading some other repositories to operate it. I don't like the idea of having to download other packages just to run a browser. The last time I did something similar was when I downloaded aMule, and that ended up being a bad idea.
Really, the best alternative for you is to use Firefox, whether 2 or 3, but with some adjustments in the about:config page. It's open-source for a reason. Take advantage of the customization.
Now, to get extensions running on Firefox 3, here's what you need to do:
1. First, after you download the tarball (http://www.mozilla.com/en-US/firefox/all-beta.html
), extract the folder inside of it, rename it something (I chose "firefox3") and put it in your Home directory. Inside that folder, click on the file named "firefox" and select "Run".
2. Open about:config, right-click, and add two new booleans: extensions.checkCompatibility (with a value of false) and extensions.checkUpdateSecurity (I originally gave this a value of false - I've since switched the value back to true, and have added new extensions without a problem, so I'm not sure how necessary this is).
3. Go into the .mozilla folder in your Home directory and copy the Firefox extensions in the extensions folder, then paste them into the extensions folder of your Firefox 3 directory.
After that, all your extensions should be working fine. Keep in mind, however, that that depends on what extensions you're using. Personally, I'm using the following, all of them working:
Add to Search Bar
User Agent Switcher