The main purpose of this post is to shortly describe the three open source alternatives to Firefox I mentioned above and give a quick overview in what are they good and in what they aren't.
The main principle behind epiphany is (for good or bad) KISS (keep it simple, stupid) which already suggests in what it might be good and in what it might not. It's a very lightweight browser with a rather simple UI, it has a reasonable set of extensions (like AdBlock or Certificates management), search (via google) implemented in location bar, it's fast and very well integrated in gnome. On the flip side, it does not save session unless it crashes. Which is a major pita, but last time I checked, the authors were against implementing it. And thanks to it using webkitgtk engine, it supports html5 youtube (you'll need Fedora 13 version of webkitgtk, the one in Fedora 12 is too old). Alas, with the switch to webkit from gecko support for ftp were dropped, java is not (yet) supported, and some of the features (like password saving, or managing certificates) stopped working, but it's steadily getting better and I believe in Gnome 2.30, there will be no regressions compared to the older gecko version and tons of new features.
Another lightweight webkitgtk based webbrowser. As it uses same engine like epiphany, many things that I said about epiphany can be said about midori too — it's fast, it supports html5 youtube, java does not work, ftp protocol is not supported, web auth is integrated with gnome-keyring (thanks to libsoup backend) and it has the awesome webinspector. In addition, it comes with session saving, adblock, trash can for closed tabs, spellchecking in multiple languages, identity masking, and quite powerful means for UI optimizing (like it can hide menu bar, can display tabs on side as a list, can disable close button on tabs [they can be closed with middle-click], can hide status bar — location bar is then used for showing the hyperlinks destination, ...). And to add to that, it has customizable search implemented into its location bar – not only you can can search what you want on whatever search engine you've added, but you can also use keywords (e.g. when I write "j 友達" it will show me the word in jisho, "gi fedora" will redirect me to google images search for fedora etc.).
I could probably go on with this praise — after all midori is the web browser that suits my needs best and has the most usable / effective UI (IMHO) that I've come across.
Well, I guess this one does not need much introduction. It's the opensource version of Google Chrome, it's based on webkit/chromium port, has a really simplistic, effective and usable UI — unless you open too many tabs. Then it becomes hell none of the zillions extension helped me out of. Plus, as the UI is heavily customized, it does not fit very well into gnome desktop, but I'd say it's really well designed. As I already mentioned, there are zillions of extensions (probably less than for firefox but still too much for me to be able to know even a tiny fraction of them) which can improve the already very good browser, and among which is not missing adblock and flashblock ;-) I quite fancy the xkcd view one. And like with other webkit based browsers — awesome webinspector, awesome speed, but also no ftp and java. Session saving and tabs undeleting is a sure thing, the already mentioned "magic location bar" works similarly like in midori.
It's possible to get html5 youtube working, but not with Fedora packages (for understandable reasons; I suspect though, that after it matures enough to get into fedora proper repos, there'll appear also something like chromium-nonfree in rpmfusion to fix that).
(note about the chromium title bar — if I cannot have chromium looking nice with plain gtk, I'll at least look at something that I fancy ;-))