Expect to order parts for it since it's not a KX or other popular selling bike, but it is indeed a bike model that has been perfected for years. 4 stroke behavior at 2 stroke maintainence cost... That's my observation.
I agree that any bike takes maintainence, though. If you're putting around, a KDX shouldn't need touched for several years (besides chain tension and changing oil/radiator fluid). If you're going to ride it often and hard, though, expect to follow some manual procedures and rebuild it once in awhile like any other bike.
What Feanor says about 4-strokes is true! Much harder to tune and work on!