I was very happy with my K20 - same sensor as your K7. As the price of the K5 came down, the more content I was with the K20 - for some reason. I was just prepared to pass the K5 over to a large extent. I had saved the funds, then one morning I saw a store over in California had apparently a pricing error (it was low and they were an authorized Pentax dealer), and I just ordered (I didn't even think about it - just dialed the telephone) - and they delivered the camera.
For the targeted reasons you listed (noise, shadows, high ISO) the camera delivers. Also it provided lower ISO at 80 with suburb dynamic range. If you are going to be doing landscapes, scenery, beaches, sunsets, etc., then in my opinion it would be well worth it. You really can't go wrong - especially if you can afford it and have the funds available.
Now that I have used it for a few weeks - was my idea of skipping it reasonable. Well its replacement has not been announced, so we have no idea as in possible improvements. Am I happy and pleased - Yes. Will I feel the need to even consider the replacement - not really unless it makes me an Ansel Adams - an that is not likely....
Also, like Liukaitc observed, the price will be higher, and since the K5 stated at $1,700 I would think that it would be that high or a bit higher. Thus, a new K5 (with a Pentax extended warranty) or wait a good year and a half. With the K5's history I wanted the extended warranty's additional piece of mind (which pushed me to new).