I rode it back to back with my older 2005 Honda Hornet 599 or CB600F... as you'd expect, there are some differences...
The KTM's WP suspension is much better suited to handle anything, from mid-turn, to absorbing bad roads very well.
By the numbers, the 990 SMT should have just 20% more power, at about the same weight, but it feels like it has more power at 3,000 rpm than the Hornet at 8,000 and it is much more abrupt.
Everything about power delivery is abrupt on the KTM. Probably because it is a big V-Twin and has lots of torque - by comparison, the Honda is tame and silky-smooth. The 990 doesn't feel well on choppy roads for instance, if you don't have a steady throttle hand.
The KTM is considerabky taller, with a seat height of 850 mm vs I think about 790 for the 599... I can touch both feet on the Honda, but just one on the KTM. The really tall position in the KTM is also more comfortable, as is the seat. I'm used to taller bikes from my dirt biking adventures, so it's ok.
The one thing that surprised me is how very flickable the taller KTM really is! I don't know if it's because is so tall, but it is pretty much just as easy to flick into the turn as the Hornet is. I didn't expect this, since the Hornet is derived from a Supersport bike.
As bad as the Givi screen is, is better than not having much protection at all, as on the naked Hornet.
2013-11-22 update. I absolutely love the KTM 990. Slipping the rear at will, on asphalt, is awesome. There are tons of power everywhere on the rev range. It has it's quirks, but I kind of like it like this... nervous and brutal. I no longer want to tame it via injection mapping.
The V-Twin with the medium-loud pipes is an awesome combination. Some friends just beg me to fire it up when they visit, just to hear it roar... I cured the loudness with some ear plugs. Not kidding...
What else - the rev limited is nuts, like everything else on this bike. I hit it in the middle of a turn and almost crashed! It brainlessly cuts the power, which, given the massive compression of two half-litre cylinders, is the same as slamming on the brakes, mid-turn.