Try July of *last year*. Epiphany has been WebKit-based for 15 months now, starting with 2.19.6: http://blogs.gnome.org/epiphany/2007/07/30/epiphany-2196-released-webkit-bac...
I was also referring to the Nokia Internet Tablets, which are known to also use WebKit (though not Epiphany, AFAIK).
Maemo (as of the current build, 4.1 - Note the lack of any major browser upgrade mention in the release notes: http://tablets-dev.nokia.com/4.1/maemo-sdk-relnotes_4.1.txt) still ships with MicroB, which is Gecko based. No other browser is installed by default, though there were apparently multiple successful ports released in 2007 (one based on Epiphany) - Not sure how mature they are/can't vouch for 'em. While I'm pleasantly surprised to learn that I was (partially) wrong about the status of Webkit in Epiphany, it is still a build option that is considered to be in beta status. Perhaps I'm misreading your statement, but if you meant to imply that Webkit was used by default in Ephiphany or Maemo, I believe you were mistaken.
Epiphany's most recent release notes seem to back up the above - http://blogs.gnome.org/epiphany/ Luckily I am wrong about the CVS thing - It's further along than that - but my core point that it wasn't quite ready for primetime and wouldn't be present in any stable distro's binaries is still likely true. If major distros are compiling in webkit, though, that's great - The more choice the better. Are they? And if you do compile in Webkit support does it still compile in Gecko support and let you switch back and forth?
More importantly for Leo's question, is it faster/substantially more efficient than an optimized Firefox config?
Sean Crago Kathmandu