First off, The few times I've had to use Factory Warranty service it all went perfectly. One was a DOA s7, promptly replaced with a new one (yes I checked it out) after they got the dead one in China. 3 other times were dead boards, all promptly replaced.

Still, that said: Their Warranty policy is my prime complaint with them.
Specifically:
1) cost. Cheapest UPS International to them for 1 hash board was around $90. The DOA s7 - $140. Ouch.
2) The Declared Value for Customs issue. This is HUGE.
I understand *why* they say to declare under US $40. It's to drastically speed up processing into China. However if the package goes a-wandering... Yer boned.

Point-2 is why I now always use Bitmain Warranty in CO for repairs - even for miners still under Factory Warranty. Yes BW in CO is strictly PAID service however even with me having a board insured for full value of $450 it still only cost $25 to ship it to them. Don't care that a typ repair cost is around $140, full value coverage is worth it.