Check out KTMTALK on fb. They have problems I didn't know could exist. They are mostly enduro and offrode bikes. The 4 strokes are plagued with all kinds of strange problem and expensive services. The 2 strokes are kick ass.
Again, you have some info from the past. I'm almost 2 years on my ktm 500 exc, over 200 hours off-road not a single issues, some guy Aaron riding same bike RTW trip close to 1000 hours , Adam Riemann same bike 3 over 7k km enduro trips not a single problem - they're rock solid machines. Actually the new 2 strokes TPI are the ones with some problems. Sure small issues you can always find on any bike, myself had some electrical problems and posted this on ktmtalk, nothing you cannot fixed yourself.