Like I said before Jayman, whaty do you see an Adv bike being used for?
The 640 Adv really tries to be a tourer, and for some people this can work, its rougher than a KLR, butthe big tank is a major plus. But if its just to ride short distances on tar to an offroad spot, mix it up in the rough stuff and then back, look at the LC4-Enduro or Suzuki DRZ400.
For the person who wants one bike for everything, offroad, road, touring, commuting, etc, the KTM 640 Adv is the best bike out there.
Take away the gnarly offroad requirement and there are better choices.
I sometimes think the KTM 640 is the best bike for my riding uses, and only the fear of being stuck 500km into Mozambique on a bike that I cant fix is the stumbling block.
That and the cost of doing anything to it.
I have done a KLR up to be what I need for about the same price as an out of the box KTM, but its basically 100% now, only falls short of the KTM offroad. The suspension is the flaw but I have another bike for offroad riding so I dont need my DS bike to do that.