I loved my 640 Adventure. Rode the wheels off it, figuratively. And while it did suck to ride a long ways on pavement, it was worth the misery if one had ridden the entire opposite direction of the trip on dirt. Like from CA to UT. Or PDX to Hyder (returned a long way on the ferry!)
The 640 was so rewarding to ride if one could "man up" and twist the throttle when things got rough. And yet so punishing if one were to try to creep up a steep rock garden or chop the throttle in sand.
Even shod in barely legal knobbies, it would dominate the (mostly) paved goaty roads around here, leaving every other rider in the dust and providing the inspiration and planted control that one didn't mind sliding on the gravel around blind corners with a drop off on one side. You could always get out of a jam on that bike, if you were willing to twist the throttle.
Sadly, my riding style and schedule changed to the point were it was making more dust in the garage than anywhere else. So I sold it.
What made the 640ADV so attractive was it's power, weight, suspension, range and minimalistic construction. I can't tell if the Norden will be the same, but if it is.... I might be in the market soon...