I've tried hard to resist but now feel I should add my story...
I bought a 1 month old DA* 50-135 lens which, as it transpired, was a warranty replacement for a 2 month old lens that had had an SDM failure. I didn't know this at the time I purchased it but I had effectively bought a new lens that according to the seller hadn't been used at all.
Upon unpacking the lens and as the seller said, it appeared to be brand new. I mounted the new lens and sadly immediately found that focusing was problematic. There was no movement at all at first but then it seemed to free up after some manual winding of the focus ring throughout its range. Not right.
I sent this second lens in for warranty repair and after 2 months it was returned to me with "motor replaced" in the report. So two new lenses each with SDM failures from new - failures clearly not related to wear or abuse but rather just design/manufacturing failures. Not a good start!
Anyway, to cut to the chase this second (now repaired) lens also failed (absolutely stone dead focussing) on its very first outing so it was returned again under warranty.
This time CRK substituted a brand new lens this time instead of another repair attempt so I can't possibly complain about the service I guess apart from the 2 month initial repair period which really seemed excessive. The actual time on the bench could surely have only been a few hours at most.
I've had this 3rd lens a few weeks but haven't had an oportunity to mount it for an outing yet. Time will tell how it goes but I'm strangely resigned to wasting my $AUD1000 on it.