I have a km and have played with the kx, both great cameras. One thing that I don't like are that there is no viewfinder indication of which auto focus point is being used, generally not much of an issue usually shooting center anyway but can be annoying when tracking moving targets. Also the lack of hard buttons. Especially for metering and auto focus modes. I really like how the K10/20D are laid out. In fact im considering selling my km to pickup a k10d I found for only 350$. Im not a very experienced photographer but I find myself switching between spot and area metering alot and center and multi point auto focus these options are all menu based on km/kx. I would love the K7 but not im my price range.
You can assign the green button, next to your right index finger, to do center-AF point.
When it is set up like this, you push that with your index finger, then push the 4-way pad with your thumb, and focus, no extra button pushing. You have a maximum of 3 quick button pushes to reach any focus point (green, and 2 direction pushes), and you always know where you are when you push the green button. You don't have to push OK or anything.
Worked pretty well for some action shots I was taking.
As for changing the metering method, I find it pretty simple especially now that the e-dial can change the setting when hovering over it. Hit info, go to metering, move e-dial. To change again, hit info, move e-dial. Works with any setting including auto-focus mode (though I pretty much only use select AF point). If you set green button to center focus, using the e-dial switches between modes. Then hit info and its still on metering mode, use e-dial to change that.
Also, the main things I missed when moving from K10D that I used for a while to K-x is 2 dials and weathersealing. I used the second dial to change ISO a lot.
However, with the newer interface of the K-x, I find it a non issue. You add one extra button - right d-pad button goes instantly to ISO. And you can use the e-dial then to change the ISO (either max ISO if auto ISO is selected or the fixed ISO).
If you can't afford the K-7 and you really need the extra buttons plus focuspoint indicator I think the K20d will be a better buy than the K10d, K20d prices have come down a lot.