Many, many years ago (maybe 1997), I started using KDE and Netscape 4 on Linux. Talk about ugly .... I tried to use KDE's browser (Don't remember if it was Konqueror back then or not) whenever possible to keep the number of loaded libraries low, but I found Netscape necessary a lot of the time. When Mozilla nightlies became usable, I switched to those instead of Netscape, but those days were the dark time on the Internet, when too many sites only worked in IE4 and 5.
In Thailand, I switched from Mandrake to LinuxTLE, a local, Thai-language distro based on RH, and I was pushed into the Gnome camp. I've used Galeon and Epiphany for the most part since then for the same reason that I used KDE's native browser when possible: It makes everything easier.
When I switched to Debian and then Ubuntu 4.10 in Korea, I started to rally for Ubuntu's default browser to be Epiphany. It's quite good, actually -- light and with a lot of good extensions, though not as many as FF.
Epiphany, on the other hand, gets all the benefits of the Gecko engine, but has several show-stopper bugs which aren't likely to get fixed for the Hardy release. These finally pushed me over to Firefox.
In the migration, though, I found one huge issue with FF3. The bookmark system changed, and I actually had to google for a few minutes to find out how to import bookmarks from a file: "Organize Bookmarks" is gone and replaced by the inscrutible "Show All Bookmarks." File > Import only works for importing from certain applications, not for files.
So, to import a file, go to Bookmarks > Show All Bookmarks and choose Import/Export. It's not quite as intuitive as one would hope (not the "Import/Export" part ... the fact that it's located in "Show All Bookmarks")
So ends my trist with the only non-default application I regularly used.