Well, I am the complete opposite - never had a problem with DSN , service is always excellent , have never had a watch that needed to be returned however I haven't bought a complete watch from him for over 18 months.
I tend to buy parts only now and find him hard to beat for this service -
His latest 2.0mm spring loaded crowns are almost 1:1 with gen
44mm custom sapphire is in a class of it's own ...along with gen
C3 hands are the closest to gen I have seen and easier than sending rep hands for a re-lume
Still stand by his 1st edition T-SWISS-T dials and his PAM 40 dial as some of the best ever 44m rep dials
Pre-A OP6500 and D series OP 6520 casebacks are pretty much 1:1 engraving , Pre-V case backs - well DSN is the only option on these and they are OK not perfect but good enough.
New 7750 correct font DW - no problems on these so far and a tad cheaper than Lello
Case gaskets , crown gaskets , replacement crown tubes , CG screws , case clamps and screws
I pity anyone who has had a bad experience and/or lost money with DSN ....but I guess so far I have been one of the lucky few.
Best
FGD