Try out this blog, he's been extensively testing the sensor and video between the K-X and K-7
Click here:
Falk Lumo
(Scroll down for a quick conclusion about the video between the K-X to the K-7)
From my internet searching, as a potential first time DSLR buyer, the video on the K-X might not have the same level of processing as the K-7, so now and then you might get aliasing with the K-X for example. But it's always hard to tell from say youtube videos, you just never now how they are getting processed by youtube or altered by the user.
For the K-X, there was a short period where it was feared you couldn't lock the auto exposure for video, causing it to adjust as you record. But there's a button on the back top right that by default it set to an auto focus button, but going into the menu, you can change it so does auto exposure lock.
I hope one day a video comparison will be done to see how much the shake reduction helps the jello video effect common on DSLR cameras.