The weather-sealed Pentax DSLRs are the K10D, K200D, K20D, K-7 and K-5. Only a few lenses are weather-resistant: the DA 18-55 WR, the DA 50-200 WR, the DA 18-135 WR, the DA 100/2.8 Macro WR and the five DA * lenses. In most cases, the kit lens sold with the K-7 and K-5 is the DA 18-55 WR, but some retailers sneak in the ordinary version to advertise a cheaper price.
The K-r and other entry-level models have a lot of preprogrammed settings for different situations, like snow or kids or flowers. The upper level cameras have only one camera-does-it-all mode; the rest of the time you have full control. The preprogrammed settings can be a nice crutch but they don't teach you anything. If you want to learn to control aperture, shutter speed and ISO yourself, both levels of camera are about the same.
I got my K-7 last year when the K-5 was not out yet, so I never had to choose between high price and high ISO, or not. I was coming from a camera that was not great above ISO 400, so the K-7 is still a big improvement for me. High ISO is always great to have as a backup, but so is a DA 55-300.
I can't make a video that I can stand to watch once myself. Until they make a camera with a talent upgrade feature, video is not important to me.