I think the saber lock is a neat idea; it would further convey that "epic struggle" feeling. Kinda reminds me of the chainsaw duels from Gears of War which I thought was awesome. We'll see if it makes it to the retail version (hopefully it does).
I do agree, something like this is always immense fun, and really adds to the experience.
It's also something that is often easily cheatable. My thumbs arn't near as fast as my friend has, and this replaces some skill with pure physical thumb mashing prowes!
It also has the problem of slowing down combat, however since we already have chain-grapples and Brutal kills which do the same, I don't see that as much of a problem
Something they'll have to work for, but I'll like to see it.
We recently CUT this feature in the last month. Unfortunately, the tech and balance involved didn't lend itself well to the overall multiplayer experience. It lives on in the Zeus video and did in our previous playable MP demos at E3, Gamescom, PAX, but we unfortunately had to cut it.
In the end, it's working out better for the MP game not to have it.