I have prepared an epiphany-webkit source package some time ago, and it has finally got out of NEW, thanks to the work Ganeff did this weekend on processing the queue =).
The good thing about those packages is I have patched them heavily to allow for easy parallel installation with Epiphany/Gecko, so you don’t need to give up your current browser to experiment and test Epiphany with the WebKitGTK+ backend. The gconf tree used for this package is /apps/epiphany-webkit, separate from the normal /apps/epiphany, for extra safety, but notice that your ~/.gnome2/epiphany will be shared between the Gecko and WebKit versions, even though the files used by each of them are different most of the time.
Go ahead and install the epiphany-webkit package, and have fun. Notice that if you have an already running session of Epiphany/Gecko, running epiphany-webkit will not be enough to launch Epiphany/Webkit, since Epiphany will just request that a new window be opened through D-Bus. The easiest way to test, if you just want a quick peek, is to run epiphany-webkit -p; this will run a ‘private’ instance of Epiphany/WebKit, which doesn’t touch your history, bookmarks, and passwords.
If you are feeling adventurous and want to make Epiphany/WebKit your default Epiphany you can do so using the following command, and selecting epiphany-webkit:
# update-alternatives --config epiphany-browser