Strengths: everything. You cannot kill this bike. It will allow you to go much further with less skill than any other brand of bike. Everything is of a higher quality and therefore works better, allowing you to focus more on riding the terrain than worrying about hurting the bike.
Weaknesses: the only real one in my mind is the water pump, but it's an every 10,000 - 20,000 mile issue. Everything else just comes down to does the bike feel comfortable to you when you ride it.
If you're coming from a Harley I'm assuming that every scheduled maintenance work was done by a Harley dealership. I'm not trying to be an ass, far from it. I'm just trying to determine what level of skill you have to work on a bike and most Harley owners I've encountered just take it to a dealership to be serviced.
If you can change the oil in anything then you can do most of the work on the bike. If you have good attention to detail then I daresay you can probably do 90% of the work on the bike. I was pretty comfortable only changing the oil in the bike and that's because when I grew up riding KTM dirt bikes that's all I had to do. Thanks to the OC, I've learned far more about my bike than I ever thought I could and when I find someone to show me how to check the valves I'll never take my bike back to the dealer again. There is a wealth of information about the bike here and if you are mechanically inclined at all and can pay attention, you can work on this bike, easily.
Maintenance wise you just have to be aware of what can happen, like Crashmaster said. Yes this is a high performance machine and yes you have to take care of it, but it's sort of like the difference between a Ford and a Ferrari. Both are reliable, both require work. With a Japanese brand bike you can get away with a bit more in my experience. Go further between oil changes before it starts shifting poorly, run the air filter dirtier, things like that. The KTM, being built more as a race ready bike, doesn't allow as much leeway. You can still beat on it, yes, but if you run it like a Jap bike you'll see a slight decrease in performance. Again, personal experience, and no one ever said I knew what I was talking about.
As far as babying the bike that's just the wrong idea. This bike was designed to withstand the Paris-Dakar Rally and unless you try to take it on a motocross track or ride it in a manner that's just stupid, you won't hurt it. Remember, it's a 500 pound monster, not a motocross bike. There are a lot of people here that can do things with them that I never would even attempt but they are far, far superior riders than I.
Would I buy one for what you're trying to do? Yes, in a heart beat. They are easy to work on, they perform flawlessly when maintained, but just realize that there may be times where you're doing the work yourself. If you're traveling you may not find a KTM dealer in every town like you will a Japanese brand or maybe even a BMW. That being said, in your case, I would go out and look at the BMW 1200 GS, the Triumph Explorer, and the Yamaha Super Tenere before buying one so that you have a frame of reference to which you can compare everything.