Originally posted by gramps50
Also the K-x has the anti-shake in the body, Sony and others have it in the lens so it makes their lens more expensive.
Sony has in-body image stabilisation, just as Pentax.
Originally posted by aliquis
They use a penta-mirror instead of penta-prism in the Sonys or something such and a special sensor for the live-view or whatever.
The K-x and Sony entry level models all use penta-mirrors. This concerns the brightness of the viewfinder view only and doesn't affect LV focusing speed.
Some Sony models indeed have an
extra sensor for LV, however it comes with its own compromises (follow the link and jump to "Live View").
I think it is a shame that the K-x doesn't show the AF points in the viewfinder, but it is a limitation one can easily work around. Many indeed use just the centre focus point and recompose but you can even select a specific point without taking the camera off your eye by first pressing the button that resets the AF point to the centre point and then navigate to the point you want to select. The markers in the viewfinder give you an idea where the AF points are and by counting your clicks when navigating you can manually select any AF point just fine.