10.
As the armrests support the weight of the rider's arms, steering becomes a mainly fingertip exercise with the added bonus of reduced vibration from particularly rough road surfaces. This means that tyre pressures can be kept at the recommended maximum which, in turn, minimises rolling resistance.
It always seemed rather strange to have armchair comfort and yet no armrests - now we've tried them, we wonder how we ever managed without. With all this extra comfort there's a serious risk a Roller rider might just doze off in slow-moving traffic!