A good friend of mine bought one of the first 11ants Mantis', it's a bike that has been displayed at a few bike shows in Europe, hence the 29" and 27,5"+ wheels.
Took it to a trail for it's first ride out in the cold last Saturday. The rear shock needs some adjustment and the different sized wheels aren't ideal, but it was good fun. The Rohloff hub in combination with the Gates Beltdrive is awesome, it works flawless, no matter how muddy it gets.
Very stable and the amount of grip is astonishing. A great experience. Would love to try it on my home trail with equal sized wheels one day.
Oh...the price..; 10000 usd...