My first bike was a Yamaha. It was in the beat-to-hell before I got it category. It smoked and it was a nightmare to work on. The year was 1998 (yes, I'm a relative newb) and the bike was a 1981 Yamaha XJ550 Seca. It had around 30,000 miles but it was air cooled and it had been stored outdoors. The first thing I did when I got it was change the oil. Near as I could tell this had never been done, or perhaps the oil had been changed but the filter had not? Anyway, getting the filter off required grinding tools. The bike was held together with fasteners made of cheese and it was apparent that in 1981 Yamaha had been mostly unaware of threaded fittings and captive nuts - you had to get a wrench on both sides of everything. And don't even get me started on YICS.
But somewhere along the line, Yamaha figured out the idea of using threaded fittings, some metallurgy, and how to select appropriately sized heads for their nuts and bolts. My 1992 Yamaha TDM is pretty easy to work on. The worst I can say is it has carb parts that are wear items, which is pretty annoying. But at least the carbs are really easy to remove, work on, and replace.
The Tènèrè seems like it will be easier to maintain, but ask me again in five years.