I was also thinking about making a video
but it was too late in the evening.
One thing to consider: 17-70 seems to focus a bit different than 16-50 (and probably 50-135). I checked it with fellow photographers having 16-50 and 17-70. The 16-50 lenses seemed to do less "clicks" than the 17-70 lenses on same bodies, focusing on same scene.
There are also differences between the hardware of 17-70 and 16-50: the former is KAF3 and the focusing ring turns during AF operation, while the latter is KAF2 and the focusing ring doesn't turn during AF operation. The internal mechanical differences can also be related to the slight differences of autofocusing.
By the way, Pentax SDM lenses doesn't really "swooooosh, beep", that's Cannon and Sigma HSM which does that
[YT]http://www.youtube.com/watch?v=ngUcQUchHEU[/YT]