I had the pleasure to shoot with a friend one night in the office where I work.
One side of the office is floor-to-ceiling glass windows, giving us a nice nightscape, but also problems regarding flash/light reflecting on the glass.
Since I don't have a strobist kit, I had to make do with a flood lamp (yes, a flood lamp, no funds for better gear) fitted with a varistor to control light intensity. A DS, the 18-55 and 50-200 kit lenses, and a cheap tripod compeleted my gear.
To expose for the background, we had to dim the flood lamp. Exposure was about 1-6 seconds at ISO 400, from 4.0 to 8.0 aperture. The light was dim enough that reading of a paper is not easy.
At the same low light levels, my friend's Canon 1000D + (cheap)50mm prime wouldn't lock focus. I can with any of my DS' 9 cross types (with the 18-55 kit), at both horizontal and portrait orientions.
Mind you we were shooting a static subject.
Of course you may argue the 1000D is Canon's bottom rung model, but so is mine, from 5 years ago.
I'm not here to contest or argue about other peoples experience with the Pentax AF, different situations, different needs. Just relating my personal experience.
Now for the bad news:
The tungsten light caused a lot of misfocus on my DS. It locked yes, but not in focus
.
So what's better? A K-r with (supposedly) better/faster AF, or a K-7 with the secondary light sensor for better accuracy at tungsten light?
So my experience is the complete opposite of the general notion (or urban legend if you will) that Canon/Nikon AF will at least lock within DOF, while Pentax will just hunt and quit.
P.S.
I'm not here to bash on Canon gear either, and my friend took better photos than I did