The K-7 focuses faster and better in both low light and "normal" light than previous cameras.
There are som unscientiffic yet reliable video clips on youtube showing the differences.
The screwdriven AF with K-7 and lenses like 18-55 and 16-45 is a blast. They are realy fast, and realy reliable in good light. The 18-55 focuses faster than Nikons 16-85 from nl to inf,
but i know thats not an fair comparison due to the very short focus path of the 18-55 and 16-45.
I would like to give cudos to Pentax for their lenses, because the are a lot faster than Sigmas and Tamrons screwdriven lenses! For example the Tamron 17-50 is much slower than DA18-55 and DA16-45, even though its short focus path.
But, all this doesnt compare to the silent and fast AF from Canikon. Because they are faster, quieter and much more reliable. I've been a Canon user before i went Pentax and i strongly feel Pentax is behind. But i knew that when i made the switch, so this is not a biggie for me.
What Pentax should do is release new SDM lenses (the SDM that they've secretly updated, or whatever). I hope they bought new motors even if they still name them SDM.
And they should build a completely new line of midlevel lenses to with focus motors! They could use the entire DA line and remake them with motors! That would be realy nice.
Imagine 16-45 F4 WR SDM, 55-300 WR SDM, DA 12-24 F4 WR SDM.....
Thats enough "bla bla bla" from me
Change system if you dont like Pentax AF and if its the most important thing to you. Thats the best thing to do! Canikon isnt bad! They're great. But it will cost more in comparison to get the same, as someone mentioned.