I've got a 2011 K1300S, and have just under 24,000 miles on it. June will be the two year anniversary.
It's my daily commuter, as well as day-rides and longer trips. I took it to Minnesota last year, did nearly 5,000 miles round-trip, and had a blast.
I've done several IronButt rides, including a 1500 BBG and SS2000 GOLD on that Minnesota ride (haven't done the certification paperwork on those yet though). The only thing that is custom is the Rick Meyer seat. Otherwise totally stock.
Never had any issues with it. Get the scheduled maintenance done, and no problems at all.
I love this bike. Such a sweet ride.