im driving a Tenere from 2008.
Exhaust terrible? Well I replaced mine after 2 years, but only for looks and sound. The old one is lying in the garage and I would not have a problem to use it again.
The cush drive wears out sooner, compared to other bikes, but its not that big deal. A lot of people using parts of tubes to stretch the lifetime. I changed mine after 12tkm, and it was not in a really bad shape.
Reg-connection had some problems on a special batch. Just take care of the plug above the regulator and you are good.
They did not put much grease on some bearings (headset and rear swing arm and levers to the rear damper), but also manageable and is part of some service work (headset at 20tkm).
Over all an really reliable bike. With no abuse, the engine should last 100tkm or more. Looks like some wheel bearings wearing out at 40tkm-60tkm.
I had really few problems. At 25tkm now a failure of an headset bearing (rust), but if someone
hat put some grease on it at 20tkm, it might have been ok now.
But I met someone with an really bad Tenere with a lot of problems. Looked like, when they moved the assembly to france, they had some quality problems. You might want to avoid those.