Although the ISO numbers look impressive on the Pentax, its only 1 stop over the D7000, which has an expandable ISO to 25600 and is pretty much its only "trump card".
The K5 can shoot 7fps over the D7000's 6fps but, the K5 can only do this for about 3 seconds. The D7000 is capable of 6fps for approximately 15 seconds, which for some people may be an issue, depending on how/what you shoot.
The AF system is superior on the Nikon too, with 39 focus points, compared to the Pentax's 11. The D7000 also has auto focus on its video recording feature, which the Pentax doesn't have. Not an issue for some but a handy feature none the less. I don't use the video on my D90 much, mainly because its a PITA to manually focus constantly and if memory serves you have to preset the exposure too. I would however use it on the D7000 if I had one.
The D7000 also meters with non-cpu lenses (one thing I was disappointed about my D90
)
Warehouse express has both camera bodies at £1100. For the money, the D7000 looks like the better option between the two based on the specs.
Edit:
You can download the original RAW/DNG file of the shot at 51200 ISO to view in Photoshop.
here . Just click "slow download"