Just thought I would chime in here.
This is something that has been discussed in great deal over on xbox-scene, and apparently it IS confirmed working on laptops (of course, as everyone knows VIA only).
http://forums.xbox-scene.com/index.php?showtopic=630969" onclick="window.open(this.href);return false;
(Sorry if we aren't allowed to post outside links)
I was hoping to give it a test run, but I haven't had any luck finding a expresscard sata card featuring a via chipset, but for the rest of you that post might have some useful information.