Ninja 400 is just fine for the highway.
Having recently moved 800 km (500 mi), I rode both my bikes, just days apart, to our new home so I can compare the experience with my N400 to my Ducati Diavel.
You will not run out of engine performance on the Ninja. It has plenty of usable power on the highway, and I overtake in 6th on the freeway. It thrums along at 7K revs and does not feel busy at all.
The Ninja has an enormously flexible engine making it easy to ride, and you get to use all the performance.
My wife's N400 has the standard windscreen. I much prefer the higher bubble optional windscreen fitted to my Ninja. Not a huge difference, but noticeably less tiring. I found this a worthwhile upgrade.
What will limit you on the highway is possibly the seat. 1 hour trips - perfect. 2 hours - gotta get off to give the bot a break. Diavel has all day comfort by comparison.
My Ninja will get a new seat to turn it into an all day ride. It is the only criticism I have with this fantastic machine.
YBMMV (Your Bum Mileage May Vary)
