Notice how this dude repeats his points two or three times in the first video. He doesn't have much to say about the differences. He says the D7000 beats it in low light but, by how much, about 1% if that? You are not going to notice it. I just posted some shots I just took with my K-5 with the autofocus on at flickr here:
Flickr: Andrew Dale Richardson's Photostream
Yes the autofocus could be a little faster for shots such as the last three I posted today on flickr. I tend to keep my finger on the shutter release button and the camera on continuous focus when I am panning or tracking a fast subject and then fire when they are in my optimal range.
I was reading somewhere on this forum that Pentax has a patent where the shake reduction helps the autofocus.
It also seems to me the autofocus hunts less with the K-5 than with the K-7. It does jump and jerk slightly when I am trying to stabilize it on a target when there are things around my subject that may confuse the autofocus. I can't fault anyone for that.