It's a good bike, very capable for a big single. If considering that and not looking to off road much, then also worth considering the KTM 640 Duke2 which is lighter and an absolute hoot but not much fun to do anything more than hour long stints in the narrow saddle.
I had the bigger brother of the Tenere 660, the XTZ750 twin. It was a capable distance bike but any pretence at being an off roady was something it really wasn't suited to. I took mine off road and found it heavy, tall, ponderous, top heavy and it didn't fill me with much confidence. It was also not that well screwed together. despite keeping it under cover and looking after it, corrosion set in on all the steel bits and it was all really made up from their low budget bin. It also suffered the same fate as a lot of big Yam motors of that era which used sodium filled valve stems and 5 valves per cylinder....valves stretched and burnt out and I had to have top end rebuilds on that and my (then) FJ1100. Put me right off buying another.
The better bikes imho (and it is just an opinion) were the KLE650 (bullet proof and great off road) and the rarer Suzuki DR650 big thumper. Better made than the Yams, reliable and great fun off road as well as on. I know several people who've gone around the world on DR650's. Saying that, the XTZ660 I think was a better bike than the early 750 super tens. Lighter and a genuine dual sport. For my money, I'd have the DR650 given the choice or for more road oriented work why not consider the DL650 weeStrom? I bought one cheaply quite recently and it's been a revelation. Simple but well made, tough, smooth torquey motor and all day comfortable.